var height=0; 
    var width=0; 
    if (self.screen) { // for NN4 and IE4 
         width = screen.width 
          height = screen.height 
    } 
    else if (self.java) { // for NN3 with enabled Java 
          var jkit = java.awt.Toolkit.getDefaultToolkit(); 
          var scrsize = jkit.getScreenSize(); 
          width = scrsize.width; 
          height = scrsize.height;
    } 

   function chk_res(ideal_width, ideal_height)  {

        if (ideal_width != width || ideal_height != height) {
           alert("This site is best viewed with IE4+ or Netscape 4+ in 800x600 resolution.");
        }

   }