diff --git a/css/style.css b/css/style.css
index a570897..7f70adc 100644
--- a/css/style.css
+++ b/css/style.css
@@ -24,103 +24,6 @@ body {
   color: #d66c79;
 }
 
-.ribbon > a {
-  display: inline-block;
-  position: absolute;
-  top: 3em;
-  right: -0em;
-  transform: rotate(30deg);
-  -webkit-transform: rotate(30deg);
-  -moz-transform: rotate(30deg);
-  -ms-transform: rotate(30deg);
-  -o-transform: rotate(30deg);
-  text-align: center;
-  box-shadow: 0 0.15em 0.25em 0 rgb(0 0 0 / 50%);
-}
-
-.ribbon > a:before {
-  content: '';
-  position: absolute;
-  width: 3em;
-  bottom: -0.5em;
-  left: -2em;
-  z-index: -2;
-  border: 1.5em solid #4490d0;
-  border-left-color: transparent;
-}
-
-.ribbon > a:after {
-  content: '';
-  position: absolute;
-  width: 3em;
-  bottom: -0.5em;
-  right: -2em;
-  z-index: -2;
-  border: 1.5em solid #4490d0;
-  border-right-color: transparent;
-}
-
-.ribbon > a > div {
-  display: inline-block;
-  position: relative;
-  margin: 0;
-  padding: 0 1em;
-  line-height: 3em;
-  color: #FFF;
-  font-weight: bold;
-  background: #337ab7;
-  text-shadow: 0 -0.08em rgb(0 0 0 / 50%);
-}
-
-.ribbon > a > div:before {
-  position: absolute;
-  content: '';
-  top: 100%;
-  left: 0;
-  border: none;
-  border-bottom: solid 0.5em transparent;
-  border-right: solid 1em #225099;
-}
-
-.ribbon > a > div:after {
-  position: absolute;
-  content: '';
-  top: 100%;
-  right: 0;
-  border: none;
-  border-bottom: solid 0.5em transparent;
-  border-left: solid 1em #225099;
-}
-
-.ribbon > a:hover:before,
-.ribbon > a:focus:before {
-  border-color: #f0778a;
-  border-left-color: transparent;
-}
-
-.ribbon > a:hover:after,
-.ribbon > a:focus:after {
-  border-color: #f0778a;
-  border-right-color: transparent;
-}
-
-.ribbon > a:hover > div,
-.ribbon > a:focus > div {
-  color: #FFF;
-  background: #d66c79;
-  text-decoration: none;
-}
-
-.ribbon > a:hover > div:before,
-.ribbon > a:focus > div:before {
-  border-right-color: #c0626c;
-}
-
-.ribbon > a:hover > div:after,
-.ribbon > a:focus > div:after {
-  border-left-color: #c0626c;
-}
-
 footer .copyright {
 	text-align: center;
 }
diff --git a/index.html b/index.html
index e171147..60ff7a9 100644
--- a/index.html
+++ b/index.html
@@ -58,11 +58,6 @@
             </div>
             <!-- /.navbar-collapse -->
         </div>
-        <div class="ribbon">
-            <a href="haskell-day-2021/">
-                <div>Haskell Day 2021 開催決定!</div>
-            </a>
-        </div>
         <!-- /.container -->
     </nav>
     <!-- Page Content -->