text-indent: -999em; /* Hide the text, works in most modern browsers */
/* --- Needed for IE --- */
font-size: 0px; /* works well in IE7. still a black line (basically the text) in IE6. */
display: block; /* Negative text-indent works in IE(6? worked fine in 7) only if this is added. */
line-height: 0px; /* Another fix for IE6. */