function checkForm()
{
	var elementArray = new Array("lastname","email");
	var errorElements = checkEmpty(elementArray);
	var errorMessage='';
	if(errorElements.length != 0)
	{
		for(var k=0;k < errorElements.length;k++)
		{
			if(errorElements[k] == 'lastname')
			{
				errorMessage += 'Gelieve uw naam in te vullen\n';
			}
			else if(errorElements[k] == 'email')
			{
				errorMessage += 'Gelieve uw e-mailadres in te vullen\n';
			}
		}
	}
	if(!errorMessage)
	{
		return true;	
	}
	alert(errorMessage);
	return false;
}

function checkEmpty(elementNames)
{
	var errorElements = new Array();
	var j=0;
	for(var i=0;i<elementNames.length;i++)
	{
		if(document.getElementById(elementNames[i]).value=='')
		{
			errorElements[j] = elementNames[i];
			j++;
		}
	}
	return errorElements;
}