function createRequestObject() { 

   var req; 

   if(window.XMLHttpRequest){ 
	  // Firefox, Safari, Opera... 
	  req = new XMLHttpRequest(); 
   } else if(window.ActiveXObject) { 
	  // Internet Explorer 5+ 
	  req = new ActiveXObject("Microsoft.XMLHTTP"); 
   } else { 
	  // There is an error creating the object, 
	  // just as an old browser is being used. 
	  alert('Problem creating the XMLHttpRequest object');
   } 

   return req; 

} 

// Make the XMLHttpRequest object 
var screenshot = createRequestObject();
	
function ActualizaScreenshot(ID_categoria, ID_proyecto, ID_screenshot) { 

   // Open PHP script for requests 
   screenshot.open("GET", 'includes/functions/ajax_screenshot.php?ID_categoria='+ID_categoria+'&ID_proyecto='+ID_proyecto+'&ID_screenshot='+ID_screenshot+'&rnd='+Math.random()); 
   screenshot.onreadystatechange = RespuestaScreenshot;
   screenshot.send(null); 
		
}

function RespuestaScreenshot() { 

   if(screenshot.readyState == 4 && screenshot.status == 200){ 

	  // Text returned FROM the PHP script 
	  var respuesta_screenshot = screenshot.responseText; 

	  if(respuesta_screenshot) { 
		 // UPDATE ajaxTest content 
		 document.getElementById("screenshot").innerHTML = respuesta_screenshot; 
	  } 

   } 

}