var currIndex = 0;

function NextCurtain()
{
    var allImages = $(".mainImg")
    var allTeasers = $(".teaser")
    allImages.hide();
    allTeasers.hide();
    currIndex++;
    if (currIndex >= allImages.length) currIndex = 0;    
    allImages.eq(currIndex).show();
    allTeasers.eq(currIndex).show();
}

function PrevCurtain()
{
    var allImages = $(".mainImg")
    var allTeasers = $(".teaser")
    allImages.hide();
    allTeasers.hide();
    currIndex--;
    if (currIndex <= -1) currIndex = allImages.length-1;
    allImages.eq(currIndex).show();
    allTeasers.eq(currIndex).show();
}