Nice for a change: a piece of code that does work in all versions of IE, but not in Firefox. I'm stuck.

Code:
<img alt="Loodgieters" title="Loodgieters" src="/core/loodgieters_uit.png" name="loodgieters" 
          border="0" style="margin-right:1px; margin-top:1px; float:left; cursor:pointer;" 
          onclick="document.location='/pages/loodgieters.php';" 
          onmouseover="foto1.style.backgroundColor='#392d63'; loodgieters.src='/core/loodgieters_aan.png'" 
          onmouseout ="foto1.style.backgroundColor='#008ac9'; loodgieters.src='/core/loodgieters_uit.png'" />
Explanation: element "loodgieters" is a menu button that should change on mouseover. It doesn't in FF, it does in IE.
Secondly, when you "mousover" the image, it should change the backgroundcolor of a second element (foto1).

Element 'foto1' is a table cell. In return, when you mouse-over this table cell, the image element 'loodgieters' should change as well. So it's a two-way thing. The code for the table cell is:

Code:
<td height="189" id="foto1" bgcolor="#008ac9" valign="top" 
	onmouseover="style.backgroundColor='#392d63'; loodgieters.src='/core/loodgieters_aan.png';" 
	onmouseout="style.backgroundColor='#008ac9';  loodgieters.src='/core/loodgieters_uit.png';" 
	style="cursor:pointer;" 
	onclick="document.location='/pages/loodgieters.php';">
	<img alt="Loodgieters" title="Loodgieters" src="/core/loodgieters.png" 
	style="border:0; margin-left:auto; margin-right:auto; margin-top:10px; display: block;" /></td>
Again: it all works as I expected in IE, Safari and Chrome, but it does not in Firefox.

The whole page validates as XHTML 1.0 Transitional
What am I overlooking here? I'm stuck. Any help is welcome