add this to your input box
HTML Code:
value="username" onfocus="if(this.value=='username')this.value=' ';" onblur="if(this.value==' ')this.value='username';"
it changes the input text dynamicly if you click inside it the value is blank if you click away and the input is blank it goes back to username. also in your css add the :focus psuedo-class so it works in all IE versions.