I have similar link structures on some pages, but they all worked fine in 3.6.x and they still work fine in 4.0.1. Sorry I can't help.

That center DIV has a z-index of -1 and that causes the layout DIV to overlay that full section. Leave that z-index at the default (1) or use a positive value like you do elsewhere.

.centerpnl {
  position: absolute; 
	left: 155px; 
	top: 0; 
	width: 660px; 
	height: 740px; /***/
	z-index: -1;
	background-color: transparent;
}

That worked! But I am puzzled. Inside the div centerpnl are others that position the various elements. They are z-index -1. W3C says, "An element with greater stack order is always in front of an element with a lower stack order". So the containing block is now in front of its contents. Its background-color is transparent so you see through it.

The sidebar men has a z-index of 5 so it is "in front" of the centerpnl contents when it slides out, and that works.

The problem affected Gecko browsers, but not Opera and IE8 so they must handle this differently. And why should it matter, a link is a link. If you can see it, it should work. If I get my z-indexes wrong I expect display problems not vanished links on buttons that I can see! And now the z-index sequence seems illogical.

Puzzling, nevertheless I am very grateful for the answer. :-)

Firefox 3 versions do not recognize negative z-index values (and probably interpret them as 1), but Firefox 4 does honor negative values, so any container with a higher or default z-index (1) that covers that part makes it impossible to click buttons. Firefox doesn't make it possible to click through layers and only the top layer receives events.

Thanks for that cor-el. This was version 3.6.17. I looked at the z-indexes again and they were inconsistent to start with so I am fixing that, and your solution worked on my local server so I m sure I shall get this right. Your explanation makes this understandable.

I have noted inconsistent interpretation of x-indexes between browsers in other contexts in te past. Thanks again.

I have same problem but do not use any z-index values. Links next to each other just are not recognized in FF7, but they are in IE9.