String.prototype.Trim = function() 
{ 
    return this.replace(/(^\s*)|(\s*$)/g, ""); 
}
function FrontPage_Form1_Validator()
{
    var email = document.getElementById("tbEmail");
    if(email.value.Trim()!="")
    {
        var pattern = /^([a-zA-Z0-9_-])+@([a-zA-Z0-9_-])+(\.[a-zA-Z0-9_-])+/; 
        var flag = pattern.test(email.value.Trim()); 
        if(!flag)
        {
            alert("incorrect email format!");
            email.focus();
            return false;
        }
        else
            return true;
    }
    else
    {
        alert("email is mandatory");
        return false;
    }
}