diff --git a/a11y.js b/a11y.js
index 9e868f2..19e9de0 100644
--- a/a11y.js
+++ b/a11y.js
@@ -2,7 +2,7 @@
 
 const a11yChecker = () => {
 
-  const getElement = (element) => document.getElementsByTagName(element);
+  const getElement = (element) => document.querySelectorAll(element);
   
   const checkDoctype = (() => {
     const doctype = document.doctype;
@@ -69,10 +69,44 @@ const a11yChecker = () => {
       const heading = getElement('h1');
       const headingLength = heading.length;
       if (headingLength > 1) {
-          console.warn('Should h1 exist in page once usually in warno!')
+          console.warn('Should h1 exist in page once usually in logo!')
       }
   })();
 
+  const checkDocumentOutline = (() => {
+    const allHeadings = [...getElement('h1, h2, h3, h4, h5, h6')];
+    const allHeadingNode= allHeadings.map(ele => ele.nodeName);
+    const uniqueHeadings = allHeadings.filter((item, pos) => allHeadingNode.indexOf(item.nodeName) === pos );
+    const headingsLength = uniqueHeadings.length;
+    
+    if (headingsLength >= 1) {
+      if (uniqueHeadings[0].nodeName !== 'H1') {
+        console.warn('Should heading start with H1:h6')
+      }
+    }
+    if (headingsLength >= 2) {
+      if (uniqueHeadings[1].nodeName !== 'H2') {
+        console.warn('Should using H2 after H1 not any heading else.')
+      }    
+    }
+    if (headingsLength >= 3) { 
+      if (uniqueHeadings[2].nodeName !== 'H3') {
+        console.warn('Should using H3 after H2 not any heading else.')
+      }
+    }
+    if (headingsLength >= 4) {
+      if (uniqueHeadings[3].nodeName !== 'H4') {
+        console.warn('Should using H4 after H3 not any heading else.')
+      }
+    }
+    if (headingsLength >= 5) {
+      if (uniqueHeadings[4].nodeName !== 'H5') {
+        console.warn('Should using H5 after H4 not any heading else.')
+      }
+    }
+  })();
+  
+
   const checkImages = (() => {
       const img = getElement('img');
       for (let i = 0; i < img.length; i++) {
@@ -419,5 +453,6 @@ code: ${allElements[i].outerHTML}`)
       }
     }
   })();
+
 }
 window.addEventListener('load', a11yChecker);
\ No newline at end of file
diff --git a/a11y.min.js b/a11y.min.js
index 85ffe89..d6f0b4a 100644
--- a/a11y.min.js
+++ b/a11y.min.js
@@ -1,4 +1,4 @@
-"use strict";const a=()=>{const a=a=>document.getElementsByTagName(a);(()=>{const a=document.doctype;if(a){const b=a.name;"html"!==b.toLowerCase()&&console.warn("Should add doctype to document!")}else console.warn("Should add doctype to document!")})(),(()=>{const b=a("html")[0];if(b)if(b.hasAttribute("lang")){const a=b.getAttribute("lang");null!==a&&""!==a||console.warn("Should add lang=value attribute to html element!")}else console.warn("Should add lang attribute to html element!")})(),(()=>{const b=a("meta")[0];b?b.hasAttribute("charset")||console.warn("Should add meta charset=utf-8 to document!"):console.warn("Should add meta charset=utf-8 to document!")})(),(()=>{const a=document.title;null!==a&&""!==a||console.warn("Should add title to describe the page content!")})(),(()=>{const b=a("link");for(let c=0;c<b.length;c++){const a=b[c].getAttribute("rel");if("stylesheet"===a)if(b[c].hasAttribute("media")>=0){const a=b[c].getAttribute("media");"print"!==a&&console.warn("Should add print style file to document.")}else console.warn("Should add print style file to document.")}})(),(()=>{const b=a("h1"),c=b.length;c>1&&console.warn("Should h1 exist in page once usually in warno!")})(),(()=>{const b=a("img");for(let c=0;c<b.length;c++)if(b[c].hasAttribute("src")){const a=b[c].getAttribute("src");null!==a&&""!==a||console.warn(`Should add src=value to the image.
+"use strict";const a=()=>{const a=a=>document.querySelectorAll(a);(()=>{const a=document.doctype;if(a){const b=a.name;"html"!==b.toLowerCase()&&console.warn("Should add doctype to document!")}else console.warn("Should add doctype to document!")})(),(()=>{const b=a("html")[0];if(b)if(b.hasAttribute("lang")){const a=b.getAttribute("lang");null!==a&&""!==a||console.warn("Should add lang=value attribute to html element!")}else console.warn("Should add lang attribute to html element!")})(),(()=>{const b=a("meta")[0];b?b.hasAttribute("charset")||console.warn("Should add meta charset=utf-8 to document!"):console.warn("Should add meta charset=utf-8 to document!")})(),(()=>{const a=document.title;null!==a&&""!==a||console.warn("Should add title to describe the page content!")})(),(()=>{const b=a("link");for(let c=0;c<b.length;c++){const a=b[c].getAttribute("rel");if("stylesheet"===a)if(b[c].hasAttribute("media")>=0){const a=b[c].getAttribute("media");"print"!==a&&console.warn("Should add print style file to document.")}else console.warn("Should add print style file to document.")}})(),(()=>{const b=a("h1"),c=b.length;c>1&&console.warn("Should h1 exist in page once usually in logo!")})(),(()=>{const b=[...a("h1, h2, h3, h4, h5, h6")],c=b.map(a=>a.nodeName),d=b.filter((a,b)=>c.indexOf(a.nodeName)===b),e=d.length;e>=1&&"H1"!==d[0].nodeName&&console.warn("Should heading start with H1:h6"),e>=2&&"H2"!==d[1].nodeName&&console.warn("Should using H2 after H1 not any heading else."),e>=3&&"H3"!==d[2].nodeName&&console.warn("Should using H3 after H2 not any heading else."),e>=4&&"H4"!==d[3].nodeName&&console.warn("Should using H4 after H3 not any heading else."),e>=5&&"H5"!==d[4].nodeName&&console.warn("Should using H5 after H4 not any heading else.")})(),(()=>{const b=a("img");for(let c=0;c<b.length;c++)if(b[c].hasAttribute("src")){const a=b[c].getAttribute("src");null!==a&&""!==a||console.warn(`Should add src=value to the image.
 code: ${b[c].outerHTML}`),b[c].hasAttribute("alt")||console.warn(`Should add alt to the image.
 code: ${b[c].outerHTML}`)}else console.warn(`Should add src to the image.
 code: ${b[c].outerHTML}`)})(),(()=>{const b=a("a"),c=b[0],d=["skip navigation","skip nav","skip to navigation","skip main navigation","skip to content","skip to main content","skip to search","skip to sidebar"];if(c){const a=c.textContent.toLowerCase();d.indexOf(a)<0&&console.warn("Should add skip to main content link!")}for(let e=0;e<b.length;e++){const a=b[e].textContent.toLowerCase(),c=b[e].getAttribute("href"),d=["more","click","click here","continue","go","here","open link","open"];if(null!==c&&""!==c||console.warn(`Should add href=value to anchor tag.
diff --git a/test.html b/test.html
index 78ca8b1..5ef3440 100644
--- a/test.html
+++ b/test.html
@@ -19,6 +19,7 @@ <h1>A11y checker</h1>
 <a href="#hi">hi</a>
 <section id="section1" class="section-prim">
   <h1>accessability checker!</h1>
+  <h3>testing issues in HTML code.</h3>
   <nav id="sec-nav" class="nav-sec">
       <button id="btn-prim" class="btn-prim"></button>
       <ul>