The position of the gallery on your web page is entirely dependent on the code that you use on your page.
If the gallery is the only element on the page, it will be displayed relative to the top-left corner (just like any other <div> container would be).
Please post the URL to your web page so that I can take a look. Thank you.

Maybe there is another <div> that is causing your gallery to be pushed down the page.
If so, then you could try using a CSS float or display: inline-block;.
Try one of the following. (Without seeing your web page I do not know if this will help.)

<div id="juicebox-container" style="float: left;"></div>
<div id="juicebox-container" style="float: right;"></div>
<div id="juicebox-container" style="display: inline-block;"></div>

You can set screenMode="SMALL" (in JuiceboxBuilder-Pro's 'Customize -> General' section) to force the gallery to be displayed in Small Screen Mode in all browsers and on all devices.
However, it sounds like you might want to try embedding the gallery in your page and, rather than just using a text link as I suggested above, set showSplashPage="ALWAYS". This will display the Splash Page which is like a large image link for your gallery. When the Splash Page is clicked, the gallery will open fullscreen. When the user clicks the 'Close Gallery' button on the Button Bar, the user will return to the original page with the Splash Page.
More information about Screen Modes and the Splash Page can be found here.

Thank you for reporting this problem.
I have been able to replicate the problem in Mobile Safari in iOS 8.4.1 using only autoPlayOnLoad="TRUE".
It does not seem to affect Mobile Safari in iOS 6.1.6 or Chrome in either iOS 6.1.6 or 8.4.1.
I have logged a bug report with the developers.

This shouldn't be the case and I cannot replicate this myself. Please post the URL to your gallery so that I can take a look at it for myself and please let me know what browser and version of iOS you see the problem in. Thank you.

You're welcome!

When using a Multi-Size Image gallery, Juicebox-Pro will use the logic noted on the support page here to determine which image size to display. Please note that the 'large' images are used only in Large Screen Mode when opening images in a new window, when the gallery is expanded or on a retina display.

Thank you for your suggestion. I would encourage you to post suggestions for future versions in the Feature Requests forum thread.
This keeps all the ideas together and ensures that they are not overlooked by the developers.
Thank you.

Edit:
Many thanks for posting your suggestion in the Feature Requests forum thread.

We do not always send out a newsletter for each new release but we do announce new versions with a Tweet.
Follow us on Twitter and you'll be notified of new releases: https://twitter.com/juiceboxgallery
Otherwise, keep an eye on the Version History page which is updated when a new version is released.

If you have imported your galleries into Showkase, then you can upgrade all your Juicebox-Pro galleries at once by following the instructions here.

If you do not use Showkase and have multiple galleries on your web site, you can have all your galleries share a single 'jbcore' folder. You can then upgrade all your galleries at once by replacing this single instance of the 'jbcore' folder on your web server.
Please see here for details.

Just follow the instructions here. After you have republished your site in Step #5, all Juicebox-Pro galleries within your Showkase site will be the version of Juicebox-Pro you upgraded to.

The current version of Showkase (v1.3.6) will work fine if you upgrade it to Juicebox-Pro v1.4.4.1.

You can certainly import Juicebox-Pro galleries created by the Lightroom plugin.
Please note that no matter what version of Juicebox-Pro the galleries are that you import, after importing, they will become the version that Showkase uses (so just upgrade Showkase to use Juicebox-Pro v1.4.4.1 and all the Juicebox-Pro galleries within your Showkase site will use this version).

Please post the URL to your main web page so that I can take a look at the problem (and the code that you are using) for myself.
If would be much easier to troubleshoot if I can see the problem live on your web server. (I'm really not sure what might be causing your problem but once I see your web page, I should hopefully have a better idea of what's going on.)
Thank you.

It looks like the problem may be that you are hard-coding your  main domain in the paths in the embedding code but that you are visiting your web site via your 'www' subdomain.

Please see this FAQ which holds the key to solving your problem:
My gallery works on 'www.example.com' but not on 'example.com' (or vice versa). Why?

Try using the following <script> section in your embedding code and your gallery should work on both your main domain and your 'www' subdomain.

<script src="/Product_Gallery/jbcore/juicebox.js"></script>
<script>
    new juicebox({
        containerId: "juicebox-container",
        baseUrl: "/Product_Gallery/",
        galleryWidth: "100%",
        galleryHeight: "100%",
        backgroundColor: "rgba(255,255,255,1)"
    });
</script>

(The leading slashes in the paths denote your root directory.)

You're welcome!
I'm glad you've got it working. Thank you for posting back to let me know.

When using relative paths, they should be relative to the page containing the gallery's embedding code so the paths you suggested should work fine:

<script src="galleries/american2/jbcore/juicebox.js"></script>
<script>
    new juicebox({
        containerId: "juicebox-container",
        baseUrl: "galleries/american2/",
        galleryWidth: "816",
        galleryHeight: "575",
        backgroundColor: "rgba(92,92,92,1)"
    });
</script>

You could also use a leading slash in your paths to denote that the paths start at the root directory so the following should also work fine:

<script src="/galleries/american2/jbcore/juicebox.js"></script>
<script>
    new juicebox({
        containerId: "juicebox-container",
        baseUrl: "/galleries/american2/",
        galleryWidth: "816",
        galleryHeight: "575",
        backgroundColor: "rgba(92,92,92,1)"
    });
</script>

When using a baseUrl, it does not matter where on your web server you upload your gallery folder to (it does not need to be uploaded to the root directory) as long as the two paths in the embedding code (the path to the 'juicebox.js' file and the baseUrl itself, pointing towards the gallery folder) are correct. Your current web site structure is fine.

Please try either of the embedding code <script> sections above. Both should work fine.

Please see this forum post regarding making galleries responsive.

Your gallery is already responsive. Its dimensions change when the browser window is made narrower and the gallery elements adjust correspondingly (for example, fewer thumbnails are displayed in a narrow browser window).

Please note that the gallery's height does not change when you change the width of the browser window.
It is not standard behavior for a div's height and width to both change when a browser window is resized in only one dimension.
If you want your gallery's aspect ratio to always remain constant, then you would have to implement a solution such as the one in this forum post.

A Juicebox-Pro gallery uses the same set of configuration options for both Small Screen Mode (SSM) and Large Screen Mode (LSM). It is not possible to have two different sets of values and switch between them and it is not possible to change configuration option values once a gallery has been loaded. The gallery would need to be reloaded with new values.
Technically, you could load the gallery, check whether SSM or LSM is being used (via the Juicebox-Pro API getScreenMode() method) and then reload the gallery using a specifc XML file corresponding to the screen mode being used. However, this is not an ideal solution.

There are some configuration options which are specific to the different screen modes (e.g. showThumbsOnLoad is for LSM only whereas showSmallThumbsOnLoad is for SSM only) but other options such as buttonBarIconSize apply equally to both SSM and LSM.

If you want to configure Juicebox-Pro beyond what can be achieved with the available configuration options, you can certainly try modifying the 'jbcore/classic/theme.css' file. However, knowledge of CSS would be required and such modifications would not be officially supported. Also, you might find that you run into unforeseen problems as Juicebox will not know of any modifications made to this file and if any changes that you make alter the size or position of any gallery elements, there may be unwanted knock-on effects with regard to the gallery layout.

Here are a few other notes which may help.

Unfortunately, the frameWidth configuration option is LSM only.

Please see this forum thread.

You can check how your gallery looks in SSM by setting screenMode="SMALL" in JuiceboxBuilder-Pro's 'Customize -> General' section.

If you find there are things that you would like to do that currently cannot be done (or at least not easily), then please post your suggestions in the Feature Requests forum thread. This keeps all the ideas together and ensures that they are not overlooked by the developers. Thank you.

OK. I'm glad everything is fine. Thank you for letting me know.

For others reading this thread, it sounds like the original poster may be referring to the Splash Page which is used by default when the gallery is embedded in a page alongside other content and displayed in Small Screen Mode.
For more information on the Splash Page and Screen Modes, please see here.