window.onload = function(){
  var yzmObj = document.getElementById("yzm");
   yzmObj.onblur=checkeyzm;
   function checkeyzm()
  {
   var yzmValue = yzmObj.value;
   var msg ="<img src='./css/ok.gif'>";
   if(!yzmValue)
      msg = "<img src='./css/err.gif'><font color='red'  size='1px'>请输验证码!</font>";

	   else if (yzmValue!=)
    msg = "<img src='./css/err.gif'><font color='red'  size='1px'>验证码错误!</font>";
	
   var span = document.getElementById("yzmcode");
   span.innerHTML = msg;
   
   
  }
 }