var typ;

Home1=new Image ();
Home1.src="http://www.carart.ch/images/"+"button_Home_off.gif";
Home2=new Image ();
Home2.src="http://www.carart.ch/images/"+"button_Home_on.gif";

function wechsel1(typ)
{
 switch (typ)
    {
     case "Home":
     window.document.Home.src=Home2.src;
     break;
    }
}

function wechsel2(typ)
{
 switch (typ)
    {
     case "Home":
     window.document.Home.src=Home1.src;
     break;
    }
}