function toggle(id,switch='on') {
	
	// Get the element
	e = document.getElementById(id);
	
	// Determine on/off
	if (switch=='on') {
		c = '#eee';
	} else {
		c = 'none';
	}
	
	// If element exists, change the style accordingly
	if (e) {
		e.style.background = c;
	}
return;
}


///// then call it this way
<ul onmouseover="toggle('about'); onmouseout="toggle('about','off');">