function resize () {
var navida = document.getElementById("sidebar").style.visibility;
  if (  navida == "visible"){
    document.getElementById("sidebar").style.visibility = "hidden";
    document.getElementById("main").style.left = "0";
    document.getElementById("main").style.width = document.body.offsetWidth+"px";
    }else{
    document.getElementById("sidebar").style.visibility = "visible";
    document.getElementById("main").style.left = "240px";
    document.getElementById("main").style.width = document.body.offsetWidth-240+"px";
    }
  }
 
function contentMax () {
document.getElementById("main").style.width = document.body.offsetWidth-240+"px";
}