Had an issue using wordpress in IE6 where the searchform.php had the following line:
<input type="submit" id="searchsubmit" value="Search" />
I changed this to:
<button id="searchsubmit" type="Search">Search</button>
and used the following css:
#searchsubmit {
	background:url(img/search-button.gif) no-repeat;
	width:67px;
	height:19px;
	text-indent:-9999px;
	cursor:pointer;
}
Removing Text Submit Button IE6 CSS
Thanks @halamoodie for this handy tip