function centrar_div(div_name){
	div = document.getElementById(div_name);
	
	div_height = div.offsetHeight;
	//alert("div_height: " + div_height);
	div_width = div.offsetWidth;
	//alert("div_width: " + div_width);
	
	display_height = window.innerHeight;
	if(!display_height) display_height = document.body.clientHeight;
	//alert("display_height: " + display_height);
	display_width = window.innerWidth;
	if(!display_width) display_width = document.body.clientWidth;
	//alert("display_width: " + display_width); 
	
	div_top = Math.round( (display_height/2) - (parseInt(div_height)/2) );
	//alert("div_top: " + div_top);
	if (div_top < 0) div_top = 0;
	
	div_left = Math.round( (display_width/2) - (parseInt(div_width)/2) );
	//alert("div_left: " + div_left);
	if (div_left < 0) div_left = 0;
	
	div.style.top = div_top;
	div.style.left = div_left;
}