sfHover = function() {
	if( document.getElementById("main_nav") ) {
		var sfEls = document.getElementById("main_nav").getElementsByTagName("li");
		for (var i=0; i<sfEls.length; i++) {
			sfEls[i].onmouseover=function() {
				this.className+=" sfhover";
				document.getElementById('truck').style.visibility="hidden";
			}
			sfEls[i].onmouseout=function() {
				this.className=this.className.replace(new RegExp(" sfhover\\b"), "");
				document.getElementById('truck').style.visibility="";
			}
		}
	}
}
if (window.attachEvent) window.attachEvent("onload", sfHover);