var DOM  = document.getElementById;
var text = "Optimal";
var x = screen.width;
var y = screen.height;
var Mass = x + " x " + y;
document.write(Mass.bold());
var i=2;

function tip() {
if (DOM && x<=640) i=1;
if (DOM && x<=800 && x>640) i=2;
if (DOM && x<=1024 && x>800) i=3;
if (DOM && x>1024) i=3;

 document.getElementById("desktop").getElementsByTagName("th")[i].innerHTML=text;
 document.getElementsByTagName("col")[i].style.background='#f0f0e5';
}