var key = randomString();
var verCode = '';

function showImg(){
document.write('<img src="http://www.lctrk.com/imgverify/img.asp?imgcode='+key+'">');
}

function setVerCode(ipt){
	verCode = ipt.value;
}

function randomString() {
	var chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXTZabcdefghiklmnopqrstuvwxyz";
	var string_length = 7;
	var randomstring = '';
	for (var i=0; i<string_length; i++) {
		var rnum = Math.floor(Math.random() * chars.length);
		randomstring += chars.substring(rnum,rnum+1);
	}
	return randomstring;
}

function chkVerCode(frm){
	if (verCode!=key){
		alert('verification code does not match');
		return false;
	}
	return true;
}