Something

// the functionfunction set_value_toggle(t) {	default_value = t.value;		t.addEvent('focus', function() { 		if (t.value == default_value) t.value = '';	});		t.addEvent('blur', function() { 		if (t.value == '') t.value = default_value;	});}// the callwindow.addEvent('domready', function() {	set_value_toggle($('desired_username'));});// the form<input class="textfield" name="desired_username" id="desired_username" type="text" tabindex="4" value="desired username" />