$(document).ready(function() {
//attach function to input and make text grayed out on page load
textReplacement($('#query').css("color", "#999"));
});

// the function:
	function textReplacement(input){ //input focus text function
 	var originalvalue = input.val();
 	input.focus( function(){
  		if( $.trim(input.val()) == originalvalue ){ input.val('').css("color", "#000"); }
 	});
 	input.blur( function(){
  		if( $.trim(input.val()) == '' ){ input.val(originalvalue).css("color", "#999"); }
 	});
}

clear textfield value, replace

jQuery