/**
* Checks if the elements with the class "required"
* are set (not empty). If failed, it give a alert.
* If succes, the form is submitted.
*
* @param form myForm a handle to an form element
*/
function checkRequiredFields(myForm)
{
	for(var idx=0; idx<myForm.elements.length; idx++)
	{
		var element = myForm.elements[idx];
		if(element)
		{
			var className = element.className;
			if(className.indexOf("required") != -1 && element.value == "")
			{
				alert("Om uw bericht goed te kunnen behandelen, is het belangrijk dat alle velden ingevuld zijn.");
				return;
			}
		}
	}
	myForm.submit();
	return;
}