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;
    			if(typeof callback == 'function') callback();
    		}
    	}
    }else{ //others
    	script.onload = function(){ 
    		if(typeof callback == 'function') callback();
    	}
    }
    script.src = url;
    document.getElementsByTagName("head")[0].appendChild(script);
}