Use simple button instead of form in error pages

data/error.html

@@ -68,12 +68,10 @@ description {
             <h1>{title}</h1>
             <p id="message">{message}</p>
             <p id="description">{description}</p>
-            <form onsubmit="location.reload()">
-                <button>
+            <button onclick="location.reload()">
                 <img src="{stock}/gtk-refresh"/>
                 <span>{tryagain}</span>
             </button>
-            </form>
         </div>
         <br style="clear: both;"/>
     </div>