If the problem is not consistent, then this suggests that the issue may lie with either your web server or internet connection.
The code on your web page remains constant so, all being well, the page should be rendered consistently by browsers each time it is loaded. However, if there is a problem with the gallery files not being served to the browser in a timely manner, then the gallery could fail to display.

Also, please ensure that you are always accessing the gallery over wi-fi rather than a 3G or 4G connection.
If you are trying to view the gallery over 3G or 4G, the gallery may fail to display. Please see this FAQ for a solution to this problem:
Why can't I view my gallery on a 3G mobile connection?

Just for the record, I have just viewed your gallery on an iOS device and the gallery's Splash Page displays fine.

However, I notice that your web page contains a few HTML errors.
It would be wise to fix them as some browsers may be more tolerant towards errors than others.
You can check the code on your web page with the W3C Markup Validation Service and then fix the errors reported.
Once the code on your web page validates correctly, your web page should be rendered with greater consistency and predictability across different browsers.