var numkey = Math.random(999);
		numkey = Math.round(numkey*10000);
		function ReSet()
		{
			numkey = Math.random(999);
			numkey = Math.round(numkey*10000);
			checkcode.innerHTML = "<img src='/checkImage.aspx?k="+numkey+"' width='52px'; height='20px'; onclick='ReSet();' alt='看不清？换一张'>";
		}
		
		function _Submit()
		{
			if(theForm.username)
			{
				if(theForm.username.value == "")
				{
					alert("请输入用户名！");
					theForm.username.focus();
					return false;
				}
			}
			if(theForm.password)
			{
				if(theForm.password.value == "")
				{
					alert("请输入密码！");
					theForm.password.focus();
					return false;
				}
			}
			if(theForm.tbCode)
			{
				if(theForm.tbCode.value == "")
				{
					alert("请输入验证码！");
					theForm.tbCode.focus();
					return false;
				}
				if(theForm.tbCode.value != numkey)
				{
					alert("验证码输入有误，请重新输入！");
					theForm.tbCode.focus();
					return false;
				}
			}
			document.theForm.submit();
			return true;
		}