function prepni_l() {
    if (document.getElementById('l_column').style.display == 'none') {
        document.getElementById('l_column').style.display = 'block'
        if (document.getElementById('img')!=null)
            document.getElementById('img').style.display = 'block'
        document.getElementById('r_column').style.marginLeft = '205px'
    } else {
        document.getElementById('l_column').style.display = 'none'
        if (document.getElementById('img')!=null)
            document.getElementById('img').style.display = 'none'
        document.getElementById('r_column').style.marginLeft = '0px'
    }
}

function swapImg(imgTo, imgFrom) {
    document.images[imgTo].src=document.images[imgFrom].src
}