function doForm(f) {
var v = f.mail.value;
var url = '/proc/check.php?v='+v;
makeRequest(url);
}

function badMail() {
	obj  = document.getElementById('mail');
	obj.className = 'bad-mail';
	if(obj.value == '')
		alert('Please enter a valid email address!');
	else alert('You have entered an invalid email address!\nPlease try again.');
}

function clean () {
	obj  = document.getElementById('mail');
	obj.className = 'good-mail';
	obj.value='';
}

    function makeRequest(url) {

        var http_request = false;

        if (window.XMLHttpRequest) { 
            http_request = new XMLHttpRequest();
            if (http_request.overrideMimeType) {
                http_request.overrideMimeType('text/xml');
            }
        } else if (window.ActiveXObject) {
            try {
                http_request = new ActiveXObject("Msxml2.XMLHTTP");
            } catch (e) {
                try {
                    http_request = new ActiveXObject("Microsoft.XMLHTTP");
                } catch (e) {}
            }
        }

        if (!http_request) {
            alert('Giving up :( Cannot create an XMLHTTP instance');
            return false;
        }
        http_request.onreadystatechange = function() { alertContents(http_request); };
        http_request.open('GET', url, true);
                
        http_request.send(null);

    }

    function alertContents(http_request) {

        if (http_request.readyState == 4) {
            if (http_request.status == 200) {
                r = http_request.responseText;

		if(r=='0') badMail();
		else document.sign.submit();

		} else {
                alert('There was a problem with the request.');
            }
        }

    }