I would really need to see your gallery to try to determine the exact cause of the problem.
Please try upgrading your gallery to the latest version of SimpleViewer-Pro (v2.3.1). It certainly cannot do any harm and it will answer the question of whether or not updating will help.
Please see the Upgrading SimpleViewer-Pro page for details.
Also, if your web page contains any custom code, then please check to see if there are any HTML errors on the web page which might be contributing to the problem.
You can check the code on your web page with the W3C Markup Validation Service and then fix any errors reported.

I notice from your screenshot that you are using iOS 7. This may be the root of the problem as SimpleViewer has not been updated since iOS 7 has been released and viewport sizes and method of hiding the toolbars have changed betweeen iOS 6 and iOS 7.
I realise it does not directly address your problem but if you are looking for a more configurable HTML gallery for display on mobile devices, you might like to take a look at Juicebox which has recently had an upgrade to fix gallery sizing issues on iOS 7. (Please see the Version History.)
For more information on the differences between SimpleViewer and Juicebox (and for details on a discount off the price of Juicebox-Pro for existing SimpleViewer-Pro users), please see this SimpleViewer news article.

Here are a few things to check/try:

(1) Upgrade your galleries to SimpleViewer-Pro v2.3.1. This will ensure that any bugs which were present in previous versions but which have since been fixed are not contributing to the problem.

(2) I notice your web page includes a very old version of jQuery (v1.4.4) which is now over 3 years old.
SimpleViewer should use its own version of jQuery (bundled within the 'simpleviewer.js' file) but try upgrading your version of jQuery to the current stable version (v1.11.0) to see if this makes a difference.

(3) Your galleries seem to be embedded into an iframe and the page loaded into the iframe loads two custom CSS files ('stylesheet.css' and '/styles/layout.css').
There may be global CSS rules within these files that the SimpleViewer galleries are inheriting and which may be affecting the layout of your galleries. Try temporarily removing these CSS file (or look for CSS rules which may apply to all div, img or p tags, for example) to see if this helps.

(4) Check to see if our own sample gallery here: http://www.simpleviewer.net/simpleviewe … es/modern/
... suffers the same problem under iOS 7.
If you see the same problem in this gallery, then I can log a bug report with the developers but, unfortunately, there may be little that can be done to fix the issue until it is addressed within the SimpleViewer core files.