function Valid_EmailId(event) {
    function checkKey(b1, e) {
        if (e.keyCode == 13) {
            document.getElementById(Head_top1_b1).click();
            return false;
        }
    }

    if (emptyField(document.getElementById("Head_top1_txtEmail"))) {
        alert('Please enter email id');
        return false;
    }
    else {
        if (emailid_format(document.getElementById("Head_top1_txtEmail").value) == false) {
            alert('Enter valid email id');
            document.getElementById("Head_top1_txtEmail").select();
            document.getElementById("Head_top1_txtEmail").focus();
            return false;
        }
    }
    var tval = (screen.height - 100) / 2;
    var lval = (screen.width - 400) / 2;
    var win = window.open('ViewMsg.aspx?email=' + document.getElementById("Head_top1_txtEmail").value, null, 'toolbar=0,location=0,directories=0,status=0,menubar=0,scrollbars=0,resizable=0,width=400,height=100,top=' + tval + ',left=' + lval, 'true');
    win.focus();
    return false;
}