function over(ac,id){
 var tli=document.getElementById("menu").getElementsByTagName("li");
if(ac==0){tli[id].className="on";}else{tli[id].className="";}
}

function check(){
  var obj=document.getElementById;
      if(obj("username").value.length==0){alert("您的姓名不能为空");obj("username").focus();return false;}
      if(obj("content").value.length<10){alert("您的需求内容也太短了点吧？");obj("content").focus();return false;}
}
function doSize(size){
	var obj=document.getElementById("contents");
	    obj.style.fontSize=size+'px';
}