function makeRequest(acao,id_sub) 
{
	http_request = false;
	
	if(acao != "retroca"){
	var opa = "<a href='#self' onclick=\"makeRequest('retroca','"+id_sub+"')\" class='botcat'>"+acao+" </a>";
	document.getElementById('titpagtxt').innerHTML = opa;
	}
	
	url = "select_buscas.php?acao=retroca&id_sub="+id_sub;

	if (window.XMLHttpRequest) 
	{ // Mozilla, Safari,...
		http_request = new XMLHttpRequest();
		if (http_request.overrideMimeType) 
		{
			http_request.overrideMimeType('text/xml');
			// See note below about this line
		}
	} 
	else if (window.ActiveXObject)
	{ // IE
		try 
		{
			http_request = new ActiveXObject("Msxml2.XMLHTTP");
		} 
		catch (e)
		{
			try 
			{
				http_request = new ActiveXObject("Microsoft.XMLHTTP");
			} 
			catch (e) {}
		}
	}	
	if (!http_request) 
	{
		alert('Giving up :( Cannot create an XMLHTTP instance');
	}
	http_request.onreadystatechange = alertContents; 
	http_request.open('GET', url, true);
	http_request.send(null);
		
}

function alertContents() 
{
	var resposta_ajax;
	if (http_request.readyState == 4) 
	{ 	
		if (http_request.status == 200) 
		{ 
			document.getElementById("backtxt").innerHTML = http_request.responseText;

			
		} 
		else
		{
			alert('There was a problem with the request.'); 
		} 
	}
}