function ventanaSecundaria (URL){ 
  	arr=(window.screen.availWidth-1100)/2;
	izq=(window.screen.availHeight-750)/2;
	window.open(URL,"cursos","width=1100,height=825,top=" + arr + ", left=" + izq + ",toolbar=no, status=no, scrollbars=yes, resizable=no,titlebar=yes") 
} 


function ventanaSecundaria2 (URL){ 
  	arr=(window.screen.availWidth-930)/2;
	izq=(window.screen.availHeight-550)/2;
	window.open(URL,"cursos1","width=810,height=800,top=" + arr + ", left=" + izq + ",toolbar=no, status=no, scrollbars=yes, resizable=no,titlebar=yes") 
}