Problems upgrading to Firefox 3

Invalid Null Pointer Error relating to DesignMode and ContentEditable

I finally upgraded to Firefox 3 the other day on my work PC but only after I managed to fix an annoying bug that had suddenly appeared in my CMS WYSIWYG editor when I had upgraded at home.

The bug was occurring whenever I closed my editor (display:none;) and then re-opened it again on the same page. I finally tracked down the bug and it was related to code that initialises the editor on opening where it sets designmode and contentEditable on. In Firefox 2 this didn't seem to cause any problems if these properties had previously been set but in FF3 it caused invalid null pointer errors. A quick check to make sure I wasn't trying to set something on that was already on fixed this problem e.g:

if(self.IE && theIframe.contentWindow.document.body.contentEditable!=true){
 theIframe.contentWindow.document.body.contentEditable = true;
}
if(!self.IE && theIframe.contentWindow.document.designMode!="on" ){
 //in moz you cannot change desgin mode straight away so try and then retry
 try{
  theIframe.contentWindow.document.designMode = "on";
  theIframe.contentWindow.document.execCommand("redo", false, null);
 }catch(e){
  setTimeout(function(){self.MakeEditable(theID);},250);
  return false;
 }
}

UserAgentButton is null Error in Firefox 3

Anyway I upgraded to Firefox 3 and then I started getting these "UserAgentButton is null" errors appear on my main site all over the place. The error in Firebug was referring to lines in my own code so it was quite confusing at first as I do not have any code that mentions UserAgentButton.

I disabled Firebug and still the problem persisted until I remembered I had installed another add on the other day that allows you switch useragent. The plug in is called "User Agent Switcher" version 0.6.11 and is very useful for testing sites. After disabling this add on the problem went away. So if you see a similar problem try disabling any add ons first before spending any time debugging your code.


Flash Not Playing Movies Correctly

Another problem I came across after upgrading to FF3 was with Flash movies not playing correctly. They would start playing but only for a few seconds before stopping and freezing.
The problem was definitely related to FF3 as they played correctly in IE and other browsers.
I read a lot of "fixes" for this problem on the web but the only thing that worked successfully
for me was to upgrade Flash to version 10.

I am not sure what other problems will come up and surprise me but the flash problem alone was reason enough not to make FF3 a level 1 supported browser on my main site. If anyone else has come across any issues relating to upgrading to Firefox 3 please let me know.