No longer use img elements changed by js for the night mode toggle button. Use a css background on the <a>. Less JS is better JS.

public/css/style-night.css

@@ -66,3 +66,7 @@ a {
 .dropdown-menu > li > a:focus, .dropdown-menu > li > a:hover {
 	background: #263238;
 }
+/* Night mode switcher  */
+#mainmenu a.nightswitch {
+    background-image: url(/img/moon.png);
+}

public/css/style.css

@@ -1,7 +1,4 @@
-/* Night mode switcher  */
-.nightswitch > img {
-    width: 24px;
-}
+
 
 /* Torrent status colors */
 .remake {
@@ -319,3 +316,11 @@ div.container div.blockBody:nth-of-type(2) table tr:first-of-type th:last-of-typ
   background: #fff;
   min-height: 460px;
 }
+/* Night mode switcher  */
+#mainmenu a.nightswitch {
+    background: transparent url(/img/sun.png) no-repeat;
+    background-size: 24px;
+    margin-top: 10px;
+    margin-left: 3px;
+    width: 24px;
+}

public/js/main.js

@@ -2,17 +2,14 @@
 var night = localStorage.getItem("night");
 if (night == "true") {
     $("head").append('<link id="style-dark" rel="stylesheet" type="text/css" href="/css/style-night.css">');
-    $("#nighticon")[0].src = "/img/sun.png";
 }
 
 function toggleNightMode() {
     var night = localStorage.getItem("night");
     if(night == "true") {
         $("#style-dark")[0].remove()
-        $("#nighticon")[0].src = "/img/moon.png";
     } else {
         $("head").append('<link id="style-dark" rel="stylesheet" type="text/css" href="/css/style-night.css">');
-        $("#nighticon")[0].src = "/img/sun.png";
     }
     localStorage.setItem("night", (night == "true") ? "false" : "true");
 }

templates/index.html

@@ -39,7 +39,7 @@
                       <span class="icon-bar"></span>
                   </button>
                   <a class="navbar-brand" href="{{.URL.Parse "/"}}">Nyaa Pantsu</a>
-                  <a class="navbar-brand hidden-md pull-right nightswitch" href="javascript:toggleNightMode();" ><img id="nighticon" src="/img/moon.png"></a>
+                  <a class="navbar-brand hidden-md pull-right nightswitch" href="javascript:toggleNightMode();" ></a>
               </div>
               <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
                   <ul class="nav navbar-nav">