window.status not working in FireFox

[knappster]

Hi,
I have an asp:hyperlink and an asp:ImageButton on a page and in each I add the following to the attributes to change the status bar text:-

Attributes.Add("onmouseover", "javascript:window.status = 'Plan Summary';return true;")
Attributes.Add("onmouseout", "javascript:window.status = '';return true;")

This works fine in IE but in FireFox only the ImageButton changes the status bar, the Hyperlink still shows the navigation url. Anyone know why this is? I have the "Change Status Bar Text" option ticked in FireFox