var initialsubj="Check this out!";
var initialmsg="Hi,%0Athis is a really great site. I think you'll like it.%0A"+window.location;

function checkEmailAddress(field) {
    var goodEmail = field.value.match(/\b(^(\S+@).+((\.com)|(\.net)|(\.edu)|(\.mil)|(\.gov)|(\.org)|(\.info)|(\.biz)|(\.aero)|(\.coop)|(\.museum)|(\.name)|(\.pro)|(\..{2,2}))$)\b/gi);
    if (goodEmail) {
        return true;
    }
    else {
        alert('Please enter a valid address.');
        field.focus();
        field.select();
        return false;
    }
}

function mailThisUrl(emailBox) {
    if(checkEmailAddress(emailBox)){
        window.location = "mailto:"+emailBox.value+"?subject="+initialsubj+"&body="+initialmsg;
    }
}