function changeClass(id,class_name)
{
	id.className = class_name;
}
function echeck(str) {
		var at="@";
		var dot=".";
		var lat=str.indexOf(at);
		var lstr=str.length;
		var ldot=str.indexOf(dot);
		if (str.indexOf(at)==-1){
		   return false
		}

		if (str.indexOf(at)==-1 || str.indexOf(at)==0 || str.indexOf(at)==lstr){
		   return false
		}

		if (str.indexOf(dot)==-1 || str.indexOf(dot)==0 || str.indexOf(dot)==lstr){
			return false
		}

		 if (str.indexOf(at,(lat+1))!=-1){
		    return false
		 }

		 if (str.substring(lat-1,lat)==dot || str.substring(lat+1,lat+2)==dot){
		    return false
		 }

		 if (str.indexOf(dot,(lat+2))==-1){
		    return false
		 }
		
		 if (str.indexOf(" ")!=-1){
		    return false
		 }
 		 return true					
	}
function emailValidation()
{
	if(document.mail.name.value=='')
	{
		alert('please write your name!');
		document.mail.name.focus();
	}
	else if(document.mail.email.value == '')
	{
		alert('please write your email!');
		document.mail.email.focus();
	}
	else if(document.mail.email.value=='')
	{
		alert('please write your email address!');
		document.mail.email.focus();
	}
	else if(!echeck(document.mail.email.value))
	{
		alert('please write your email correctly!');
		document.mail.email.focus();
	}
	else if(document.mail.subject.value == '')
	{
		alert('write the subject!');
		document.mail.subject.focus();
	}
	else if(document.mail.text.value=='')
	{
		alert('please your email text!');
		document.mail.text.focus();
	}
	else
		document.mail.submit();
}