The Mobile Player within SimpleViewer does set the scale and lock the viewport on Android devices but it sets 'width=device-width' so the entire width of your web page should be visible across the width of your device's screen.
I notice that your gallery still uses SimpleViewer-Pro v2.1.3.
Please try upgrading your gallery to the current version of SimpleViewer-Pro (v2.3.1) to see if this makes a difference.
Many bugs have been fixed since v2.1.3 so upgrading may help. (Even if it does not help, we can then at least rule out any bugs that were present in previous versions of SimpleViewer but which have since been fixed.)
Please see the Version History for a full list of changes.
Instructions for upgrading can be found on the Upgrading SimpleViewer-Pro support page.
Also, although it is not a direct solution to your problem, you might like to try Juicebox (a different image viewer), at least to see whether or not the same problem occurs.
Juicebox is an alternative image viewer to SimpleViewer (and is more configurable on mobile devices) which uses HTML 5 rather than Adobe Flash.
For more information on the differences between SimpleViewer and Juicebox, please see this SimpleViewer news article.
You could download and try Juicebox-Lite (the free version) to see if this works any better within you web site.
If the problems persists, please let me know what Android device and browser you are using.
The more information we have, the better. Thank you.
SimpleViewer Support Team