I guess technically you could create a div that has an opacity of 0% (making it invisible) with a display of block that is absolutely positioned in the cell you want with a z-index of 99 which brings it to the top of all other items. Give it the proper width & height to fill the cell. Inside that div just create a block displayed link with width & height of 100%.
That should be about all you need to "cover" stuff up with an invisible link. Here's a small example:
<style type="text/css"><!--
td { position:relative; }
.invisiLink {
display:block;
filter:Alpha(opacity=0);
height:100%;
left:0;
margin:0;
opacity:0.0;
padding:0;
position:absolute;
top:0;
width:100%;
z-index:99;
-moz-opacity:0.0;
}
.invisiLink a, .invisiLink a:link, .invisiLink a:visited {
display:block;
height:100%;
text-decoration:none;
width:100%;
}
--></style>
<table>
<tr>
<td>Some text</td>
<td>Some text</td>
<td>Some text</td>
</tr>
<tr>
<td>Some text</td>
<td><a href="http://www.phpbuilder.com">PHPBuilder</a><div class="invisiLink"><a href="http://phpbuilder.bpatterson.net">PHPBuilder</a></div></td>
<td>Some text</td>
</tr>
<tr>
<td>Some text</td>
<td>Some text</td>
<td>Some text</td>
</tr>
</table>
Now, in IE you have to specify essentially the same exact contents of what you're trying to "hide". Firefox and other browsers can handle css properly 😉 The above example shows that instead of being taken to this site (phpbuilder.com) instead you'll be taken elsewhere.
Note that this works in IE, and firefox is a little messed up, but thats where you can come in to tweak the code and position it where you want.
Hope it helps 😉