function check_form(f){
	var errorItems;
	var result = true;
	var errorText = "There are errors: ";
	
	//alert("Company: " + f.company.value);
	
	if(is_blank(f.name.value)){
		errorText = errorText + "Value for Name not given. ";
		var header = document.getElementById('name_h');
		header.setAttribute("class", "error");
		result = false;
	}
	if(is_blank(f.email.value)){
		errorText = errorText + "Value for E-mail not given. ";
		var header = document.getElementById('email_h');
		header.setAttribute("class", "error");
		result = false;
	}
	if(is_blank(f.address.value)){
		errorText = errorText + "Value for Address not given. ";
		var header = document.getElementById('address_h');
		header.setAttribute("class", "error");
		result = false;
	}
	if(is_blank(f.city.value)){
		errorText = errorText + "Value for City not given. ";
		var header = document.getElementById('city_h');
		header.setAttribute("class", "error");
		result = false;
	}
	
	if (result == false){
		replaceP("warnings", errorText);
		alert(errorText);
	}
	
	return result;
}

function is_blank(s){
	for(var i = 0; i < s.length; i++){
		var c = s.charAt(i);
		if((c != ' ') && (c != '\n') && (c != '')) return false;
	}
	return true;
}

function replaceP(id, textitem){
	
	var newNode = document.createElement("p");
	newNode.setAttribute("id", id);
	
	var newText = document.createTextNode(textitem);
	newNode.appendChild(newText);
	
	var oldNode = document.getElementById(id);
	var parent = document.getElementById(id).parentNode;
	
	parent.replaceChild(newNode, oldNode);
}