Hello mackmick,

Would you try this please :
Clear the Firefox cache :
https://support.mozilla.org/en-US/kb/how-clear-firefox-cache

"Remove the cookies" from websites that cause problems :
https://support.mozilla.org/en-US/kb/delete-cookies-remove-info-websites-stored (scroll down to : "Delete cookies for a single site")

If you use extensions like Adblock Plus, NoScript, Flash Block, Ghostery, then always make sure such extensions do not block (wanted) content.

You could also check your settings here :

https://support.mozilla.org/en-US/kb/content-blocking

If none of the above do the trick, then let's Try Firefox in Safe Mode :

If Firefox is not running : Hold down the Shift key when starting Firefox.

If Firefox is running : 3-bar menu => ' ? ' (at the bottom of the dropdown) => 'Restart with Add-ons disabled'. Then OK the restart. A small dialog should appear. Click 'Start in Safe Mode' ( not 'Refresh' !)

See : https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode

And : https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

Any difference ?

Did not help.

It almost looks like my page is running in mobile mode. Minimal menus and data. But I have no idea how to control this.

PS, this is on a desktop with a very large screen.

mackmick said

It almost looks like my page is running in mobile mode. Minimal menus and data. But I have no idea how to control this.

Just to make sure : this goes for "ancestry.com" only ? Other sites are in desktop mode  ?

I am only seeing it on Ancestry but it would have to be a site that detected the machine and not adaptive mode. I am not sure how many sites use the machine detection style to switch browser modes.

Seemed to happen after the last update of FF.

mackmick said

PS, this is on a desktop with a very large screen.

Sites with "responsive" layouts may switch based on perceived/computed screen resolution or window width. You can increase the perceived/computed screen resolution and window width by maximizing the window and zooming out: hold down the Ctrl key and tap the - key once or twice.

Any changes in the layout?

Thanks I meant responsive.

This is the issue. If I stretch the window out it goes back to normal mode. But the browser size is hugh at the break point. It is 840 wide. I set my webs at 880 max. So I think Ancestry has changed something to make FF so sensitive.

I was trying to see what FF device was being selected. Any thoughts?

I was going to ask you to take a look at this :

https://developer.mozilla.org/en-US/docs/Tools/Responsive_Design_Mode

But I will leave you in the capable hands of jscher2000, who knows way more about this than I do.

mackmick said

If I stretch the window out it goes back to normal mode. But the browser size is hugh at the break point. It is 840 wide. I set my webs at 880 max.

I'm not sure what you mean. You use resizable windows no more than 880 pixels wide to keep the content a reasonable width? Or you use an add-on or other technique to override the page layout?

Each designer may have their own cutover point between phone, tablet, and desktop displays, so there's no magic number to avoid this problem that will work for every site. You might have to zoom out to get the desktop layout in a narrower window.

I use a max width of 880 just to keep the page reasonable, I guess I could go for much wider but the format becomes harder to deal with using a lot of images.

Seems going to mobile or reduced menu mode at 840 is really overkill. But I should be able to shrink content and get what I want.