diff --git a/src/footer.inc b/src/footer.inc
index cf049ee..0f5e7c6 100644
--- a/src/footer.inc
+++ b/src/footer.inc
@@ -38,7 +38,7 @@
                     #end if
                 </table>
 
-                #if $Extras.Footer.about is not ""
+                #if $Extras.Footer.about != ""
                 <p>$Extras.Footer.about</p>
                 #end if
 
@@ -50,11 +50,11 @@
             ## Grid column
             <div class="col-md-3 mb-md-0 mb-3">
 
-                #if $Extras.Footer.box_title is not ""
+                #if $Extras.Footer.box_title != ""
                 <h5 class="text-uppercase">$Extras.Footer.box_title</h5>
                 #end if
 
-                #if $Extras.Footer.box_content is not ""
+                #if $Extras.Footer.box_content != ""
                 <p>$Extras.Footer.box_content</p>
                 #end if
             </div>
@@ -67,22 +67,22 @@
                 <h5 class="text-uppercase">$Extras.Translations[$Extras.language].links</h5>
 
                 <ul class="list-unstyled">
-                    #if $Extras.Footer.link1_url is not ""
+                    #if $Extras.Footer.link1_url != ""
                     <li>
                         <a href="$Extras.Footer.link1_url" target="_blank" rel="noopener">$Extras.Footer.link1_label</a>
                     </li>
                     #end if
-                    #if $Extras.Footer.link2_url is not ""
+                    #if $Extras.Footer.link2_url != ""
                     <li>
                         <a href="$Extras.Footer.link2_url" target="_blank" rel="noopener">$Extras.Footer.link2_label</a>
                     </li>
                     #end if
-                    #if $Extras.Footer.link3_url is not ""
+                    #if $Extras.Footer.link3_url != ""
                     <li>
                         <a href="$Extras.Footer.link3_url" target="_blank" rel="noopener">$Extras.Footer.link3_label</a>
                     </li>
                     #end if
-                    #if $Extras.Footer.link4_url is not ""
+                    #if $Extras.Footer.link4_url != ""
                     <li>
                         <a href="$Extras.Footer.link4_url" target="_blank" rel="noopener">$Extras.Footer.link4_label</a>
                     </li>
@@ -118,11 +118,11 @@
           #end if
         #end if
 
-        #if $Extras.Footer.imprint_url is not ""
+        #if $Extras.Footer.imprint_url != ""
         <span class="mx-2">&bull;</span>
         <a href="$Extras.Footer.imprint_url" target="_blank">$Extras.Footer.imprint_label</a>
         #end if
-        #if $Extras.Footer.privacy_url is not ""
+        #if $Extras.Footer.privacy_url != ""
         <span class="mx-2">&bull;</span>
         <a href="$Extras.Footer.privacy_url" target="_blank">$Extras.Footer.privacy_label</a>
         #end if
diff --git a/src/head.inc b/src/head.inc
index e8c5865..e392f05 100644
--- a/src/head.inc
+++ b/src/head.inc
@@ -52,7 +52,7 @@
 
 ## Appearance settings
 
-#if $Extras.Appearance.lo_value_color is not ""
+#if $Extras.Appearance.lo_value_color != ""
 <style>
     .lo-text {
         color: $Extras.Appearance.lo_value_color !important;
@@ -60,7 +60,7 @@
 </style>
 #end if
 
-#if $Extras.Appearance.hi_value_color is not ""
+#if $Extras.Appearance.hi_value_color != ""
 <style>
     .hi-text {
         color: $Extras.Appearance.hi_value_color !important;
diff --git a/src/header.inc b/src/header.inc
index a9bbd66..3879223 100644
--- a/src/header.inc
+++ b/src/header.inc
@@ -8,7 +8,7 @@
         <span class="navbar-brand d-flex">
             #if $Extras.Header.show_logo == "yes"
             <a class="mr-2" href="index.html">
-                #if $Extras.Header.custom_logo_url is not ""
+                #if $Extras.Header.custom_logo_url != ""
                 <img src="$Extras.Header.custom_logo_url" style="width: 4rem">
                 #else
                 <img src="img/icon-alpha-1x.png" srcset="img/icon-alpha-1x.png 1x, img/icon-alpha-2x.png 2x" style="width: 4rem">
@@ -28,7 +28,7 @@
             <ul class="navbar-nav ml-auto mr-auto">
 
                 #if $Extras.Header.current_nav_link == "yes"
-                    #if $active_nav is 'current'
+                    #if $active_nav == 'current'
                     <li class="nav-item active mr-3">
                         <a class="nav-link" href="index.html">$Extras.Translations[$Extras.language].current</a>
                     </li>
@@ -40,7 +40,7 @@
                 #end if
 
                 #if $Extras.Header.yesterday_nav_link == "yes"
-                    #if $active_nav is 'yesterday'
+                    #if $active_nav == 'yesterday'
                     <li class="nav-item active mr-3">
                         <a class="nav-link" href="yesterday.html">$Extras.Translations[$Extras.language].yesterday</a>
                     </li>
@@ -52,7 +52,7 @@
                 #end if
 
                 #if $Extras.Header.week_nav_link == "yes"
-                    #if $active_nav is 'week'
+                    #if $active_nav == 'week'
                     <li class="nav-item active mr-3">
                         <a class="nav-link" href="week.html">$Extras.Translations[$Extras.language].week</a>
                     </li>
@@ -64,7 +64,7 @@
                 #end if
 
                 #if $Extras.Header.month_nav_link == "yes"
-                    #if $active_nav is 'month'
+                    #if $active_nav == 'month'
                     <li class="nav-item active mr-3">
                         <a class="nav-link" href="month.html">$Extras.Translations[$Extras.language].month</a>
                     </li>
@@ -76,7 +76,7 @@
                 #end if
 
                 #if $Extras.Header.year_nav_link == "yes"
-                    #if $active_nav is 'year'
+                    #if $active_nav == 'year'
                     <li class="nav-item active mr-3">
                         <a class="nav-link" href="year.html">$Extras.Translations[$Extras.language].year</a>
                     </li>
@@ -88,7 +88,7 @@
                 #end if
 
                 #if $Extras.Header.archive_nav_link == "yes"
-                    #if $active_nav is 'archive'
+                    #if $active_nav == 'archive'
                     <li class="nav-item active mr-3">
                         <a class="nav-link" href="archive.html">$Extras.Translations[$Extras.language].archive</a>
                     </li>
@@ -100,7 +100,7 @@
                 #end if
 
                 #if $Extras.Header.almanac_nav_link == "yes"
-                    #if $active_nav is 'almanac'
+                    #if $active_nav == 'almanac'
                     <li class="nav-item active mr-3">
                         <a class="nav-link" href="almanac.html">$Extras.Translations[$Extras.language].almanac</a>
                     </li>
@@ -111,13 +111,13 @@
                     #end if
                 #end if
 
-                #if $Extras.Header.custom1_url is not ""
+                #if $Extras.Header.custom1_url != ""
                 <li class="nav-item mr-3">
                     <a class="nav-link" href="$Extras.Header.custom1_url">$Extras.Header.custom1_label</a>
                 </li>
                 #end if
 
-                #if $Extras.Header.custom2_url is not ""
+                #if $Extras.Header.custom2_url != ""
                 <li class="nav-item mr-3">
                     <a class="nav-link" href="$Extras.Header.custom2_url">$Extras.Header.custom2_label</a>
                 </li>
diff --git a/src/index.html.tmpl b/src/index.html.tmpl
index b879c5c..23a0cf1 100644
--- a/src/index.html.tmpl
+++ b/src/index.html.tmpl
@@ -241,19 +241,19 @@ new ApexCharts(document.querySelector('#$id'), {
       name: "$getVar('obs.label.' + series1)",
       data: [ $getChartData(series1, column) ]
     }
-    #if $series2 is not "" and $getVar('day.' + series2 + '.has_data')
+    #if $series2 != "" and $getVar('day.' + series2 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series2)",
       data: [ $getChartData(series2, column) ]
     }
     #end if
-    #if $series3 is not "" and $getVar('day.' + series3 + '.has_data')
+    #if $series3 != "" and $getVar('day.' + series3 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series3)",
       data: [ $getChartData(series3, column) ]
     }
     #end if
-    #if $series4 is not "" and $getVar('day.' + series4 + '.has_data')
+    #if $series4 != "" and $getVar('day.' + series4 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series4)",
       data: [ $getChartData(series4, column) ]
diff --git a/src/month-%Y-%m.html.tmpl b/src/month-%Y-%m.html.tmpl
index cb2659e..4afb10e 100644
--- a/src/month-%Y-%m.html.tmpl
+++ b/src/month-%Y-%m.html.tmpl
@@ -233,19 +233,19 @@ new ApexCharts(document.querySelector('#$id'), {
       name: "$getVar('obs.label.' + series1) Max",
       data: [ $getChartData(series1, 'max') ]
     }
-    #if $series2 is not "" and $getVar('month.' + series2 + '.has_data')
+    #if $series2 != "" and $getVar('month.' + series2 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series2)",
       data: [ $getChartData(series2, column) ]
     }
     #end if
-    #if $series3 is not "" and $getVar('month.' + series3 + '.has_data')
+    #if $series3 != "" and $getVar('month.' + series3 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series3)",
       data: [ $getChartData(series3, column) ]
     }
     #end if
-    #if $series4 is not "" and $getVar('month.' + series4 + '.has_data')
+    #if $series4 != "" and $getVar('month.' + series4 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series4)",
       data: [ $getChartData(series4, column) ]
@@ -270,19 +270,19 @@ new ApexCharts(document.querySelector('#$id'), {
       name: "$getVar('obs.label.' + series1)",
       data: [ $getChartData(series1, column) ]
     }
-    #if $series2 is not "" and $getVar('month.' + series2 + '.has_data')
+    #if $series2 != "" and $getVar('month.' + series2 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series2)",
       data: [ $getChartData(series2, column) ]
     }
     #end if
-    #if $series3 is not "" and $getVar('month.' + series3 + '.has_data')
+    #if $series3 != "" and $getVar('month.' + series3 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series3)",
       data: [ $getChartData(series3, column) ]
     }
     #end if
-    #if $series4 is not "" and $getVar('month.' + series4 + '.has_data')
+    #if $series4 != "" and $getVar('month.' + series4 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series4)",
       data: [ $getChartData(series4, column) ]
diff --git a/src/month.html.tmpl b/src/month.html.tmpl
index 95ec374..ef16405 100644
--- a/src/month.html.tmpl
+++ b/src/month.html.tmpl
@@ -223,19 +223,19 @@ new ApexCharts(document.querySelector('#$id'), {
       name: "$getVar('obs.label.' + series1)",
       data: [ $getChartData(series1, column) ]
     }
-    #if $series2 is not "" and $getVar('month.' + series2 + '.has_data')
+    #if $series2 != "" and $getVar('month.' + series2 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series2)",
       data: [ $getChartData(series2, column) ]
     }
     #end if
-    #if $series3 is not "" and $getVar('month.' + series3 + '.has_data')
+    #if $series3 != "" and $getVar('month.' + series3 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series3)",
       data: [ $getChartData(series3, column) ]
     }
     #end if
-    #if $series4 is not "" and $getVar('month.' + series4 + '.has_data')
+    #if $series4 != "" and $getVar('month.' + series4 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series4)",
       data: [ $getChartData(series4, column) ]
diff --git a/src/week.html.tmpl b/src/week.html.tmpl
index 9a5f7c5..72cce48 100644
--- a/src/week.html.tmpl
+++ b/src/week.html.tmpl
@@ -223,19 +223,19 @@ new ApexCharts(document.querySelector('#$id'), {
       name: "$getVar('obs.label.' + series1)",
       data: [ $getChartData(series1, column) ]
     }
-    #if $series2 is not "" and $getVar('week.' + series2 + '.has_data')
+    #if $series2 != "" and $getVar('week.' + series2 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series2)",
       data: [ $getChartData(series2, column) ]
     }
     #end if
-    #if $series3 is not "" and $getVar('week.' + series3 + '.has_data')
+    #if $series3 != "" and $getVar('week.' + series3 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series3)",
       data: [ $getChartData(series3, column) ]
     }
     #end if
-    #if $series4 is not "" and $getVar('week.' + series4 + '.has_data')
+    #if $series4 != "" and $getVar('week.' + series4 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series4)",
       data: [ $getChartData(series4, column) ]
diff --git a/src/year-%Y.html.tmpl b/src/year-%Y.html.tmpl
index cf4ec44..02a0fa8 100644
--- a/src/year-%Y.html.tmpl
+++ b/src/year-%Y.html.tmpl
@@ -277,19 +277,19 @@ new ApexCharts(document.querySelector('#$id'), {
       name: "$getVar('obs.label.' + series1) $Extras.Translations[$Extras.language].max",
       data: [ $getChartData(series1, 'max') ]
     }
-    #if $series2 is not "" and $getVar('year.' + series2 + '.has_data')
+    #if $series2 != "" and $getVar('year.' + series2 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series2)",
       data: [ $getChartData(series2, column) ]
     }
     #end if
-    #if $series3 is not "" and $getVar('year.' + series3 + '.has_data')
+    #if $series3 != "" and $getVar('year.' + series3 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series3)",
       data: [ $getChartData(series3, column) ]
     }
     #end if
-    #if $series4 is not "" and $getVar('year.' + series4 + '.has_data')
+    #if $series4 != "" and $getVar('year.' + series4 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series4)",
       data: [ $getChartData(series4, column) ]
@@ -314,19 +314,19 @@ new ApexCharts(document.querySelector('#$id'), {
       name: "$getVar('obs.label.' + series1)",
       data: [ $getChartData(series1, column) ]
     }
-    #if $series2 is not "" and $getVar('year.' + series2 + '.has_data')
+    #if $series2 != "" and $getVar('year.' + series2 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series2)",
       data: [ $getChartData(series2, column) ]
     }
     #end if
-    #if $series3 is not "" and $getVar('year.' + series3 + '.has_data')
+    #if $series3 != "" and $getVar('year.' + series3 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series3)",
       data: [ $getChartData(series3, column) ]
     }
     #end if
-    #if $series4 is not "" and $getVar('year.' + series4 + '.has_data')
+    #if $series4 != "" and $getVar('year.' + series4 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series4)",
       data: [ $getChartData(series4, column) ]
diff --git a/src/year.html.tmpl b/src/year.html.tmpl
index 432d95a..8780a77 100644
--- a/src/year.html.tmpl
+++ b/src/year.html.tmpl
@@ -231,19 +231,19 @@ new ApexCharts(document.querySelector('#$id'), {
       name: "$getVar('obs.label.' + series1) $Extras.Translations[$Extras.language].max",
       data: [ $getChartData(series1, 'max') ]
     }
-    #if $series2 is not "" and $getVar('year.' + series2 + '.has_data')
+    #if $series2 != "" and $getVar('year.' + series2 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series2)",
       data: [ $getChartData(series2, column) ]
     }
     #end if
-    #if $series3 is not "" and $getVar('year.' + series3 + '.has_data')
+    #if $series3 != "" and $getVar('year.' + series3 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series3)",
       data: [ $getChartData(series3, column) ]
     }
     #end if
-    #if $series4 is not "" and $getVar('year.' + series4 + '.has_data')
+    #if $series4 != "" and $getVar('year.' + series4 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series4)",
       data: [ $getChartData(series4, column) ]
@@ -268,19 +268,19 @@ new ApexCharts(document.querySelector('#$id'), {
       name: "$getVar('obs.label.' + series1)",
       data: [ $getChartData(series1, column) ]
     }
-    #if $series2 is not "" and $getVar('year.' + series2 + '.has_data')
+    #if $series2 != "" and $getVar('year.' + series2 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series2)",
       data: [ $getChartData(series2, column) ]
     }
     #end if
-    #if $series3 is not "" and $getVar('year.' + series3 + '.has_data')
+    #if $series3 != "" and $getVar('year.' + series3 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series3)",
       data: [ $getChartData(series3, column) ]
     }
     #end if
-    #if $series4 is not "" and $getVar('year.' + series4 + '.has_data')
+    #if $series4 != "" and $getVar('year.' + series4 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series4)",
       data: [ $getChartData(series4, column) ]
diff --git a/src/yesterday.html.tmpl b/src/yesterday.html.tmpl
index 59c0aea..3c52540 100644
--- a/src/yesterday.html.tmpl
+++ b/src/yesterday.html.tmpl
@@ -213,17 +213,17 @@
 series1data = [ $getChartData(series1, column) ];
 half_length1 = Math.ceil(series1data.length / 2);
 
-#if $series2 is not ""
+#if $series2 != ""
 series2data = [ $getChartData(series2, column) ];
 half_length2 = Math.ceil(series2data.length / 2);
 #end if
 
-#if $series3 is not ""
+#if $series3 != ""
 series3data = [ $getChartData(series3, column) ];
 half_length3 = Math.ceil(series3data.length / 2);
 #end if
 
-#if $series4 is not ""
+#if $series4 != ""
 series4data = [ $getChartData(series4, column) ];
 half_length4 = Math.ceil(series4data.length / 2);
 #end if
@@ -242,19 +242,19 @@ new ApexCharts(document.querySelector('#$id'), {
       name: "$getVar('obs.label.' + series1)",
       data: series1data.splice(0,half_length1)
     }
-    #if $series2 is not "" and $getVar('yesterday.' + series2 + '.has_data')
+    #if $series2 != "" and $getVar('yesterday.' + series2 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series2)",
       data: series2data.splice(0,half_length2)
     }
     #end if
-    #if $series3 is not "" and $getVar('yesterday.' + series3 + '.has_data')
+    #if $series3 != "" and $getVar('yesterday.' + series3 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series3)",
       data: series3data.splice(0,half_length3)
     }
     #end if
-    #if $series4 is not "" and $getVar('yesterday.' + series4 + '.has_data')
+    #if $series4 != "" and $getVar('yesterday.' + series4 + '.has_data')
     ,{
       name: "$getVar('obs.label.' + series4)",
       data: series4data.splice(0,half_length4)