function c_tool() {
	fld = document.getElementById('if_url_f');
	if (fld.value == 'your url goes here...') {
		fld.value = '';
	}
}

function pop_tool() {
	fld = document.getElementById('if_url_f');
	if (fld.value == '') {
		fld.value = 'your url goes here...';
	}
}