Here are a few tips which may help.
(1) The <div id="header"> is not closed on your page. If a browser does not know where the end of the container should be, this can affect the layout of the page.
(3) The sample gallery whose code you are using sets fixed dimensions for the header and footer and then embeds the gallery in the remaining space. Try giving your gallery dimensions of 100% x 100% so that it fills the space available.
(2) The JavaScript code on your web page resizes the 'juicebox-content' container but there is no such container on your web page. Try wrapping your 'juicebox-container' <div> in a parent <div> with id="juicebox-content" so that the gallery can be resized correctly when the size of the browser window changes:
<div id="juicebox-content">
<div id="juicebox-container"></div>
</div>
(4) Try removing the <table> from your web page and use only CSS to layout your page.
If you see different images in your gallery on different computers or devices, then this can only be due to your browser caching your gallery files. Please double-check that you are completely clearing your browser's cache before reloading your gallery to ensure that your browser is fetching and using the most recent versions of your gallery files.
Please see this FAQ:
When I update my gallery I don't see my changes online. Why? - http://www.juicebox.net/support/faq/#troubleshooting-6
Hopefully this will help.