function trim(str){
		return str.replace(/^\s+|\s+$/g, '');
	}
	
	function checkEmail(email)
	{
		var filter = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
		return filter.test(email);
	}
	
	function check(f){
		//name
		if (trim(f.name.value) == ''){
			alert('Fields are empty. Please fill out all fields');

			f.name.focus();
			return false;
		}
		
		//email
		if (trim(f.email.value) == ''){
			alert('Fields are empty. Please fill out all fields');
			f.email.focus();
			return false;
		}
		
		if (!checkEmail(f.email.value)){
			alert('Write correct E-Mail!');
			f.email.focus();
			return false;
		}
		
		//message
		if (trim(f.message.value) == ''){
			alert('Fields are empty. Please fill out all fields');
			f.message.focus();
			return false;
		}
		return true;
	}