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I stole majority of this code from

http://www.aspcode.net/A-watermark-texbox-with-JQuery-and-aspnet.aspx

but I added a bit to make it swap css classes as well

$().ready(function() {   swapValues = [];   $(".wm").each(function(i) {     swapValues[i] = $(this).val();     $(this).focus(function() {       if ($(this).val() == swapValues[i]) {         $(this).val("").removeClass("watermark")       }     }).blur(function() {         if ($.trim($(this).val()) == "") { $(this).val(swapValues[i]).addClass("watermark") } }) }) }); To use it, make sure your TextBox has (one of) it's css classes set to "wm". If you want a seperate style to be applied add that initially as well, in my example, it swaps "watermark" in and out as a css class.