visibility doesn't change in netscape

[markvl]

I'm using a javascript function in which I change the visibility of an image or text contained by DIV (like <div id="img">...</div>. This works fine in IE. For NN7 I'm also using document.getElementById("img").style.visibility="visible" or ...="hidden", but it doesn't change to a new value. Either visible or hidden, the initial value hasn't changed.
It makes no difference if I 'specify' the style directly in html, a (separate) stylesheet or by javascript.
What might cause it not to work?

[gil davis]

Nothing apparent in what you posted. Something else broken in your page could cause it to not work.