Works for me in Firefox 43.

You can try these steps in case of issues with web pages:

You can reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files.

• Hold down the Shift key and left-click the Reload button
• Press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)
• Press "Command + Shift + R" (Mac)

Clear the cache and remove cookies only from websites that cause problems.

"Clear the Cache":

• Firefox/Tools > Options > Advanced > Network > Cached Web Content: "Clear Now"

"Remove Cookies" from sites causing problems:

• Firefox/Tools > Options > Privacy > "Use custom settings for history" > Cookies: "Show Cookies"

Start Firefox in Safe Mode to check if one of the extensions (Firefox menu button/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

• Switch to the DEFAULT theme: Firefox menu button/Tools > Add-ons > Appearance
• Do NOT click the Reset button on the Safe Mode start window

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

The problem occurs also in safe mode.

Firefox responded by email: "Since flash is required for Picasa Web Albums they do not work in Firefox. This embed method works:

   In your Picasa Web Album Click "Link to this album".
   Select "Embed Slideshow".
   Select the size you want.
   Copy the text in the box.
   Edit the page you want to put the album links in.
   Click the HTML button.
   Paste the text you copied above.
   Click Update.
   Save the page."

However, I cannot do this on the slideshow on my Google Drive. So I am still stuck.

Please ignore the Picasa Web Albums problem, I believe that is something completely different. I'm running Firefox 32-bit on Windows 7 64-bit and your slideshow is definitely not using Flash.

Two things you might check:

(1) I'm testing logged out. Does the problem occur if you are logged out (or using a private window) or only logged in?

(2) Does the slideshow work for you outside of the frame, in other words, if you right-click where it is, expand This Frame, and choose Open Frame in New Tab? That's how I got this link:

https://docs.google.com/presentation/d/1YlaLM6U7hJxwc_7w7a5wKuScNxYaeqKNSPT0_TgAlVc/embed?start=true&loop=false&delayms=5000

Thanks for your advice, The link you gave me at docs.google.com/presentation does bring up my slideshow, and the slideshow works fine on my Google Drive, but it doesn't work on my Google Site, even if I go to This Frame and try opening it in a new tab, new window, etc.

I hadn't noticed before that the slide show is "double framed" the outer frame is:

http://emnikv6fkkb6l1pdpikqd0dhjl15ss1c-a-sites-opensocial.googleusercontent.com/gadgets/ifr?url=https://sites.google.com/site/scriptsexamples/Presentation-to-slideshow.xml&container=enterprise&view=default&lang=en&country=ALL&sanitize=0&v=fd1e2a6bee13c84e&libs=core:setprefs&mid=63&parent=http://www.schuhplattlerkids.org/home#up_backgroundColor=white&up_url=https://docs.google.com/presentation/d/1YlaLM6U7hJxwc_7w7a5wKuScNxYaeqKNSPT0_TgAlVc/pub?start%3Dfalse%26loop%3Dfalse%26delayms%3D5000&up_autoStart=true&st=e%3DAIHE3cDrZGyw2SToBuyWSd%252BvvZBTKc0L3g8TkPuJhxU5c%252B4%252BOr50F%252FBXu2EU1kGICF%252BqOL6IY%252BcWwD%252BGf49yD2BfbaCewn3v%252BHupN4%252B02nsGCxHzL56MY7%252F%252Bu9unjxQKfOHxD8jb14r3%26c%3Denterprise&rpctoken=-9137674465727607925

Is that the one that doesn't load for you?

What does "double framed" mean? Neither of the links you just gave me give me anything more than that same brief black flash and then a blank screen. By the way, the same problem occurs on my mobile website (http://www.schuhplattlertanz.org/home) and my tablet site (http://www.schuhplattlerkinder.org/home), which worked fine last week (I think before I installed Firefox 43) and which I haven't visited in a long time. So the problem must have something to do with Firefox rather than anything on the websites.

Double framed means that your main page contains an iframe tag that incorporates another page into a rectangular area, but that incorporated page itself contains an iframe tag that incorporate a third page into a rectangular area.

The innermost page is the first link, on docs.google.com

The intermediate page is the link I gave you in the last post. That was one big long link. If it split into two links in email, please use the link on the forum page.

If that does not work when you access it directly, then your Firefox may not be able to load successfully from that intermediate server, emnikv6fkkb6l1pdpikqd0dhjl15ss1c-a-sites-opensocial.googleusercontent.com (that's a mouthful). But I don't currently have a theory as to why.

In the mobile page, the slideshow does not fit properly and only the top half of the photos is visible (this is Firefox 43 on Windows 7). I didn't check the other one.

The link did not work. However, after removing my add-ons and refreshing Firefox (which I had done earlier to no avail), the slideshows now work again. Thanks for your help.

Hmm, I wonder which setting or add-on was causing the problem? If you decide to investigate further, you can compare the files in the Old Firefox Data folder on your desktop (which contains your old pre-Refresh profile folder) with your new profile folder. I suppose if no one else mentions the problem, it might not be worth the time.