//------------------------------------------------------------------------------------------------------------------------
// проверка формы перед отправкой
//------------------------------------------------------------------------------------------------------------------------

function mailfield (str) 
{ 
	var reg = /^[0-9a-z_]+@[0-9a-z_^.]+.[a-z]{2,3}$/;
	return reg.test(str); 
}

function checkForm () 
{
	var form = "mailform";	
	var title;
	var elem;
	var dutyField  = " is empty.";
	var wrongField = " is invalid.";
	var check = true;

	function checkError (field, str) 
	{
		document.getElementById("alert").innerHTML = str;
		document.forms[form].elements[field].focus();
		check = false;
	}
	document.getElementById("alert").innerHTML = "";

    if (check)
    {
		title = '"E-mail"';
		elem = document.getElementById("email").value;
		if (elem.length == 0)      checkError('email', 'Error: ' + title + dutyField);
		else if (!mailfield(elem)) checkError('email', 'Error: ' + title + wrongField);
    }	
	
	if (check)  
	{ 
		document.forms[form].submit(); 
	}

	return check;
}