if (document.images) {
  //tlacitko b1
  b1on = new Image(188,20);
  b1on.src="./img/left_menu/m11.gif";
  b1off= new Image(188,20);
  b1off.src="./img/left_menu/m1.gif";
  
  //tlacitko b2
  b2on = new Image(188,20);
  b2on.src="./img/left_menu/m22.gif";
  b2off= new Image(188,20);
  b2off.src="./img/left_menu/m2.gif";

  //tlacitko b3
  b3on = new Image(188,20);
  b3on.src="./img/left_menu/m33.gif";
  b3off= new Image(188,20);
  b3off.src="./img/left_menu/m3.gif";

  //tlacitko b4
  b4on = new Image(188,20);
  b4on.src="./img/left_menu/m44.gif";
  b4off= new Image(188,20);
  b4off.src="./img/left_menu/m4.gif";

  //tlacitko b5
  b5on = new Image(188,20);
  b5on.src="./img/left_menu/m55.gif";
  b5off= new Image(188,20);
  b5off.src="./img/left_menu/m5.gif";

  //tlacitko b6
  b6on = new Image(188,20);
  b6on.src="./img/left_menu/m66.gif";
  b6off= new Image(188,20);
  b6off.src="./img/left_menu/m6.gif";

  //tlacitko b7
  b7on = new Image(188,20);
  b7on.src="./img/left_menu/m77.gif";
  b7off= new Image(188,20);
  b7off.src="./img/left_menu/m7.gif";

  //tlacitko b8
  b8on = new Image(188,20);
  b8on.src="./img/left_menu/m88.gif";
  b8off= new Image(188,20);
  b8off.src="./img/left_menu/m8.gif";

  //tlacitko b9
  b9on = new Image(188,20);
  b9on.src="./img/left_menu/m99.gif";
  b9off= new Image(188,20);
  b9off.src="./img/left_menu/m9.gif";

}

function hover(imgName)
{
  if (document.images) {
    imgOn=eval(imgName + "on.src");
    document[imgName].src= imgOn;
  }
}

function unhover(imgName)
{
  if (document.images) {
    imgOff=eval(imgName + "off.src");
    document[imgName].src= imgOff;
  }
}