function preload() {
    var preloaded = [];
    for (var i = 0; i < images.length; i++) {
        preloaded[i] = new Image();
        preloaded[i].src = images[i];
    }
}

function show(image) {
    var big = document.getElementById('big');
    var file = image.src.replace(/b\.jpg/, 'a.jpg');
    big.src = file;

    var thumbs = document.getElementById('thumbs');
    thumbs = thumbs.getElementsByTagName('p');
    for (var i = 0; i < thumbs.length; i++) {
        thumbs[i].style.borderColor = '#eee';
    }
    var thumb = image.parentNode.parentNode;
    thumb.style.borderColor = '#77a9c0';
}