Replace Text With An Image Using CSS

This technique works by pushing the text down inside the header with a rather large line-height (it must be at least twice the height). Then the overflow: hidden hides the text since it’s overflowing. Source

<style type="text/css">
             width: 13px;
            height: 15px;   

            overflow: hidden;
            line-height: 500px;                  

How to Override Table cellSpacing and cellPadding properties in IE6, IE7 and FireFox

This will force your table cellPadding and cellSpacing properties to 0 in Firefox, IE6, IE7, IE8.

            border-collapse: collapse;             
            *border-collapse: expression('separate', cellSpacing = '0px');  /* IE hack  */