// validate form
function validateForm(formObj){
  	valid=true;
	var title=formObj.elements[0];
	if(!title){return};
	if(!title.value){showError(title,'*Enter a title for your blog')};
	var author=formObj.elements[1];
	if(!author){return};
	if(!author.value){showError(author,'*Enter your full name')};
	var content=formObj.elements[2];
	if(!content){return};
	if(!content.value){showError(content,'*Enter some text for your blog')};
	return valid;
}
// show error messages
function showError(obj,message){
	if(!obj.errorNode){
    	obj.onchange=hideError;
    	var span=document.createElement('span');
		span.className='error';
    	span.appendChild(document.createTextNode(message));
    	obj.parentNode.appendChild(span);
   		obj.errorNode=span;
 	}
  	valid=false;
  	return
}
// hide error messages
function hideError(){
  	this.parentNode.removeChild(this.errorNode);
  	this.errorNode=null;
  	this.onchange=null;
}
// execute 'ValidateForm()' function when page is loaded
window.onload=function(){
  	// check if browser is W3CDOM compatible
  	if(document.getElementById&&document.getElementsByTagName&&document.createElement){
		var insform=document.getElementById('insertform');
		if(insform){insform.onsubmit=function(){return validateForm(this)}};
		var updform=document.getElementById('updateform');
		if(updform){updform.onsubmit=function(){return validateForm(this)}};
    }
}