function check_Valid(th)
{
	if(th.txt_name.value.length<=0)
	{
		alert("Please enter Name !");
		th.txt_name.focus();
		return false;
	}
	if(th.txt_email.value.length<=0)
	{
		alert("Please enter Email !");
		th.txt_email.focus();
		return false;
	}
	else
	{
		if(verifymail(th.txt_email)==false)
		{
			return false;
		}
	}
	if(th.txt_phone.value.length<=0)
	{
		alert("Please enter Phone Number !");
		th.txt_phone.focus();
		return false;
	}
	if(th.txt_city.value.length<=0)
	{
		alert("Please enter City !");
		th.txt_city.focus();
		return false;
	}
	if(th.description.value.length<=0)
	{
		alert("Please enter Description !");
		th.description.focus();
		return false;
	}
	
	
	return true;
}



<!------------#mail#_---------------------------!>
function verifymail(me)
{    	var stremail; 
		var validRegExp = /^\w(\.?\w)*@\w(\.?[-\w])*\.([a-z]{3}(\.[a-z]{2})?|[a-z]{2}(\.[a-z]{2})?)$/i ;

		stremail = me.value;

		if(stremail != "")
		{
			var isValid = validRegExp.test(stremail);
			if(!isValid)
			{
				alert("Invalid Email Address !");
				stremail = me.focus();
				return false;
			}
			return true;
		}
		return true;
}