I actually just did this today. It is pretty easy, open up modules/text.php, and add this on line 75:
if ($value) {
$atts .= ‘ onFocus=”if(this.value==\” . $value . ‘\’) { this.value=\’\’; }”‘;
$atts .= ‘ onBlur=”if(this.value==\’\’) { this.value=\” . $value . ‘\’; }”‘;
}
This will erase the field when they click on it if the text is still the default (i.e ‘Your Name’) and will add it back in when they click to a different field if they left it empty.