function loadScript(url, callback){
    var script = document.createElement("script");
    script.type = "text/javascript";
    if (script.readyState){  //IE
        script.onreadystatechange = function(){
            if (script.readyState == "loaded" ||
                    script.readyState == "complete"){
                script.onreadystatechange = null;
                callback();
            }
        };
    } else {  //Others
        script.onload = function(){
            callback();
        };
    }
    script.src = url;
    document.getElementsByTagName("head")[0].appendChild(script);
}



function initMainNav (){

 	$("#main_nav").find("div.default").children("a").bind("mouseover", function(){

	 	$(this).parent().addClass('hover');
	});
	$("#main_nav").find("div.default").children("a").bind("mouseout", function(){

	 	$(this).parent().removeClass('hover');
	});
}