ALT is not a tooltip

Lot's of webpages are using alt as a tooltip. Example from Overheid.nl:

<!-- reformatted -->
<a href="http://overheidsloket.overheid.nl/" 
   target="_top" 
   onmouseover="changeImage( 'nav_overheidsloket', '_over' );" 
   onmouseout="changeImage( 'nav_overheidsloket', '_out' );">
 
 <img id="nav_overheidsloket" 
      name="nav_overheidsloket" 
      src="/images/nav_overheidsloket_out.gif" 
      border="0" 
      width="175"
      height="19"
      alt="Subsidies, vergunningen, belastingen, ontheffingen...">
</a>

Besides that this code could be cleaned up a lot, the alternate text of the image isn't really chosen correctly. See it for yourself:

Does the above image read the same as: Subsidies, vergunningen, belastingen, ontheffingen..., exactly!

Better markup would be:

<a href="http://overheidsloket.overheid.nl/">
 <img src="/images/nav_overheidsloket_out.gif" 
      width="175"
      height="19"
      alt="Overheidsloket" 
      title="Subsidies, vergunningen, belastingen, ontheffingen...">
</a>

Though we wouldn't have the rollover anymore if we did it like above. Maybe it is better to use the CSS rollover technique from Petr Stanicek:

Overheidsloket

The markup is clean:

<a href="http://overheidsloket.overheid.nl/" id="css-rollover-example">Overheidsloket</a>

The style is clean:

a#css-rollover-example{
 display:block;
 width:175px;
 height:19px;
 background:url(./files/nav_overheidsloket_combined.gif) no-repeat top left;
	 
 text-indent:-100em;
 overflow:hidden;
}
 a#css-rollover-example:hover{
 background-position:0 -92px;
}

I should probably send them some feedback :-)