function checkVersion()
{
	var userAgent = window.navigator.userAgent.toLowerCase();
	var AppName = "";
	var Version = "";
	var Sys = "";
	if (userAgent.indexOf("msie")>-1) {
		AppName = "msie";	
		Version	= userAgent.replace(/.+msie/gi,"").replace(/;.+/gi,"") - 0;	
	} else if(userAgent.indexOf("firefox")>-1) {
		AppName = "firefox";
		Version = parseFloat(userAgent.replace(/.+firefox\//gi,"").replace(/\(.*\)/g,"")) - 0;
	} else if(userAgent.indexOf("netscape")>-1) {
		AppName = "netscape";
		Version = ParseFloat(userAgent.replace(/.+netscape\//gi,"").replace(/\(.*\)/g,"")) - 0;
	}

	if ((AppName == "netscape") || (AppName == "firefox" && Version < 1.5)) {
		return false;
	} 

	return true;
}

function login_check()
{
	if (checkVersion() == false) {
		alert("浏览器版本不支持，请升级到新版本!");
		return false;
	}
	if(document.login.username.value=="")  {
		alert(document.getElementById('usernamemessage').innerHTML);
		return false;
	} else if(document.login.username.value.length<1) {
		alert(document.getElementById('usernameerror').innerHTML);
		return false;
	} else if(document.login.username.value.length>30) {
		alert(document.getElementById('usernameerror').innerHTML);
		return false;
	} else if(document.login.password.value=="") {
		alert(document.getElementById('passwordmessage').innerHTML);
		return false;
	} else if(document.login.password.value.length<2) {
		alert(document.getElementById('passworderror').innerHTML);
		return false;
	} else if(document.login.password.value.length>18){
		alert(document.getElementById('passwordlength').innerHTML);
		return false;
	} else  {
		return true;
	}
}