IE8 does not have a string.trim()-function, so use regex..

src/static/js/chat.js

@@ -75,7 +75,7 @@ var chat = (function()
     send: function()
     {
       var text = $("#chatinput").val();
-      if(text.trim().length == 0)
+      if(text.replace(/\s+/,'').length == 0)
         return;
       this._pad.collabClient.sendMessage({"type": "CHAT_MESSAGE", "text": text});
       $("#chatinput").val("");