if (document.images) {
            img1on=new Image();
            img1on.src="bilder/button_home_over.gif";
            img2on=new Image();
            img2on.src="bilder/button_aerzte_over.gif";
            img3on=new Image();
            img3on.src="bilder/button_notfaelle_over.gif";
            img4on=new Image();
            img4on.src="bilder/button_igel_over.gif";
            img5on=new Image();
            img5on.src="bilder/button_journal_over.gif";
            img6on=new Image();
            img6on.src="bilder/zurueck_over.gif";
            img7on=new Image();
            img7on.src="bilder/vor_over.gif";
            img8on=new Image();
            img8on.src="bilder/button_info_over.gif";
            img9on=new Image();
            img9on.src="bilder/button_protest_over.gif";

            img1off=new Image();
            img1off.src="bilder/button_home_default.gif";
            img2off=new Image();
            img2off.src="bilder/button_aerzte_default.gif";
            img3off=new Image();
            img3off.src="bilder/button_notfaelle_default.gif";
            img4off=new Image();
            img4off.src="bilder/button_igel_default.gif";
            img5off=new Image();
            img5off.src="bilder/button_journal_default.gif";
            img6off=new Image();
            img6off.src="bilder/zurueck.gif";
            img7off=new Image();
            img7off.src="bilder/vor.gif";
            img8off=new Image();
            img8off.src="bilder/button_info_default.gif";
            img9off=new Image();
            img9off.src="bilder/button_protest_default.gif";
        }

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

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