jQuery lightbox plugin change apperance of my wordpress site

Answer 1

This would be a CSS issue. I see on your site the css:

#navback {
    background-color: #121621;
    margin-bottom: 10px;
    height: 1%;
}

change that to this:

#navback {
    background-color: #121621;
    margin-bottom: 10px;
    height: 20px;
}

and you should be golden :)