function validate_required(field,alerttxt){
	with (field) {
		if (value==null||value=="") {
			alert(alerttxt);
			return false;
		}
		else {
			return true
		}
	}
}
function validate_email(field,alerttxt) {
	with (field) {
		apos=value.indexOf("@");
		dotpos=value.lastIndexOf(".");
		if (apos<1||dotpos-apos<2)  {
			alert(alerttxt);
			return false;
		}
		else {
			return true;
		}
	}
}
function validate_form(thisform) {
	with (thisform)	{
		if (validate_required(txtUser,"Please write you name!") == false) {
			txtUser.focus();
			return false;
		} else if (validate_required(txtEmail,"Please write your Email address!") == false) {
			txtEmail.focus();
			return false;
		} else if (validate_email(txtEmail,"Uncorrect Email address format!\nExample: john@yahoo.com") == false) {
			txtEmail.focus();
			return false;
		} else if (validate_required(txtSubject,"Please write your e-mail subject!") == false) {
			txtSubject.focus();
			return false;
		} else if (validate_required(txtMessage,"Please write your message!") == false) {
			txtMessage.focus();
			return false;
		}
	}
}