hideCaption = function(){
    $('#caption').animate({
        opacity: 0
    });
}

$(document).ready(function(){
    $('#caption').css({
        opacity: 0
    });
    $('#mainpic').mouseenter(function(){
        $('#caption').animate({
            opacity: 0.3
        });
    });
    $('#mainpic').mouseleave(hideCaption);
    $('.thumb').mouseleave(hideCaption)
    $('.thumb').click(function(im){
        id = this.src.match(/([0-9]*)\.jpg/)[1];
        var i = jQuery.grep(images, function(e){
            return e.id == id;
        });
        $('#mainpic').fadeTo(200, 0, function(){
            $('#mainpic').attr({
                src: i[0].src
            }).fadeTo(200, 1);
            $('#caption').html(i[0].caption);
            $('#caption').animate({
                opacity: 0.3,
            });
        });
    });
});