var prohlizec=navigator.appName.indexOf("Netscape");
var verze=parseInt(navigator.appVersion);

  if ( (prohlizec != -1 && verze >= 3) || (verze == 4) ) {
    but1_menu = new Image(); but1_menu.src = "../pict/but1_menu.jpg";
    but2_menu = new Image(); but2_menu.src = "../pict/but2_menu.jpg";
    but1_menu_2 = new Image(); but1_menu_2.src = "../pict/but1_menu_2.jpg";
    but2_menu_2 = new Image(); but2_menu_2.src = "../pict/but2_menu_2.jpg";
    but1_menu_3 = new Image(); but1_menu_3.src = "../pict/but1_menu_3.jpg";
    but2_menu_3 = new Image(); but2_menu_3.src = "../pict/but2_menu_3.jpg";

    intro1 = new Image(); intro1.src = "pict/intro1.jpg";
    intro2 = new Image(); intro2.src = "pict/intro2.jpg";

    nav1_right = new Image(); nav1_right.src = "../pict/nav1_right.jpg";
    nav2_right = new Image(); nav2_right.src = "../pict/nav2_right.jpg";
    nav1_up = new Image(); nav1_up.src = "../pict/nav1_up.jpg";
    nav2_up = new Image(); nav2_up.src = "../pict/nav2_up.jpg";
    nav1_left = new Image(); nav1_left.src = "../pict/nav1_left.jpg";
    nav2_left = new Image(); nav2_left.src = "../pict/nav2_left.jpg";
    nav1_home = new Image(); nav1_home.src = "../pict/nav1_home.jpg";
    nav2_home = new Image(); nav2_home.src = "../pict/nav2_home.jpg";
    
  }
  function zmena(prvek,obr) {      
    if ( (prohlizec != -1 && verze >= 3) || (verze == 4) ) {
    var zdroj=eval(obr+ ".src");
    document[prvek].src = zdroj;
    }
  }