function checkform(){

	var filter  = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;   

 	if(document.requestForm.mail.value == ""){

		alert('Email field can not be left blank!');

		document.requestForm.mail.focus();

		return false;

	}

	else if(!filter.test(document.requestForm.mail.value)){

		alert('Email seems to be wrong!');

		document.requestForm.mail.focus();

		return false;

	}

	else{

		return true;

	}

}