function btnHomeClick() {
    setButtons('btnHome');
    getContent('HomeSite.htm');

}
function btnDetailsClick() {
    setButtons('btnDetails');
    getContent('DetailsSite.htm');

}

function btnAnmeldungClick() {

    setButtons('btnAnmeldung');
    getContent('AnmeldungSite.htm');
}

function btnKontaktClick() {

    setButtons('btnKontakt');
    getContent('KontaktSite.htm');

}

function setButtons(activeBtnId) {

    if (activeBtnId == 'btnHome') {
        getButton('btnHome').setAttribute('src', 'Images/Buttons/home_c.png');
    }
    else {
        getButton('btnHome').setAttribute('src', 'Images/Buttons/home.png');
    }

    if (activeBtnId == 'btnDetails') {
        getButton('btnDetails').setAttribute('src', 'Images/Buttons/details_c.png');
    }
    else {
        getButton('btnDetails').setAttribute('src', 'Images/Buttons/details.png');
    }

    if (activeBtnId == 'btnAnmeldung') {
        getButton('btnAnmeldung').setAttribute('src', 'Images/Buttons/anmeldung_c.png');
        btnAnmelden_disabled = false;
    }
    else {
        getButton('btnAnmeldung').setAttribute('src', 'Images/Buttons/anmeldung.png');
    }

    if (activeBtnId == 'btnKontakt') {
        getButton('btnKontakt').setAttribute('src', 'Images/Buttons/kontakt_c.png');
        btnKontakt_disabled = false;
    }
    else {
        getButton('btnKontakt').setAttribute('src', 'Images/Buttons/kontakt.png');
    }
}

function getButton(id) {

    return document.getElementById(id);
}