function newsCallback () {
	   if (http_request.readyState == 4) {
	     if (http_request.status == 200) {
	       var response = http_request.responseText;
	       
	       document.getElementById('ajax-articles-div').innerHTML = response;
	       document.getElementById('ajax-the-article-div').innerHTML = '';
	     } 
	   }
	}
	
	function articleView (category, pageNum,firstID) {
			if (window.XMLHttpRequest) { // Mozilla, Safari, ...
			            http_request = new XMLHttpRequest();
			        } else if (window.ActiveXObject) { // IE
			            http_request = new ActiveXObject("Microsoft.XMLHTTP");
			 }
			if (http_request)
			{
		        //seta a função de call back
		        http_request.onreadystatechange = newsCallback;
		        var url = '/articles.do?category=' + category + '&page=' + pageNum + '&firstArticleID=' + firstID;
		        http_request.open('get',url, true);
		        http_request.setRequestHeader('Content-Type','application/x-www-form-urlencoded');      
				http_request.send(null);
			}
	}
    
    
    function pageChange(category,pageNum,firstID)
    {
		if (pageNum==null)
			pageNum=1;

    	articleView(category,pageNum,firstID);
    }