Hello, this is a known problem and will be fixed in Firefox 59.

AliAlomran said

There is a website that I opened view through the FF, and I am required to zoom it to 110% for the best viewing. What I need is that I don't want to make the zooming again to 110% for this website specifically every time I opened this website. So, Is there any option in FireFox to save the Zoom for specific website and at the same time doesn't change the default zoom option for the other websites unless changed?

Yes, this is how Firefox has worked for a long time.

When is your Firefox losing track of the desired zoom level for that site?

(1) When you exit Firefox and start it up again

Make sure you have not set Firefox to clear history when it closes or, if you have that turned on, adjust its Settings:

• Windows: "3-bar" menu button (or Tools menu) > Options
• Mac: "3-bar" menu button (or Firefox menu) > Preferences
• Linux: "3-bar" menu button (or Edit menu) > Preferences
• Any system: type or paste about:preferences into the address bar and press Enter/Return to load it

In the left column, click Privacy & Security. On the right side, under History, change the selector to "Firefox will: Use custom settings for history" and observe the "Clear history when Firefox closes" line.

Either uncheck this option or if you want to use it, click the Settings button on the right side and make sure there is no check mark for "Site Preferences" since that covers your decisions about sites such as zoom levels, Flash permission, popup permission, etc.

(2) In any new tab, zooming is per tab instead of per site

There is a hidden setting that could cause this that you can remove. Note, if you do not find this setting, that means this is not the problem.

(A) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful or accepting the risk.

(B) In the search box above the list, type or paste zoom and pause while the list is filtered

(C) If the browser.zoom.siteSpecific preference is bolded and "modified" or "user set" to false, right-click > Reset it to remove this customization

Mkll said

Hello, this is a known problem and will be fixed in Firefox 59.

What is going to change in Firefox 59?

Make sure you have not set Firefox to clear history when it closes or, if you have that turned on, adjust its Settings:

• Windows: "3-bar" menu button (or Tools menu) > Options

In the left column, click Privacy & Security. On the right side, under History, change the selector to "Firefox will: Use custom settings for history" and observe the "Clear history when Firefox closes" line. Either uncheck this option or if you want to use it, click the Settings button on the right side and make sure there is no check mark for "Site Preferences" since that covers your decisions about sites such as zoom levels, Flash permission, popup permission, etc. (2) In any new tab, zooming is per tab instead of per site There is a hidden setting that could cause this that you can remove. Note, if you do not find this setting, that means this is not the problem. (A) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful or accepting the risk. (B) In the search box above the list, type or paste zoom and pause while the list is filtered (C) If the browser.zoom.siteSpecific preference is bolded and "modified" or "user set" to false, right-click > Reset it to remove this customization

The problem is that everything you suggest already is set by default but the problem is still exit

Hi AliAlomran, when do you lose the zoom level.

For example, if you open a page from the site in a second tab, does it have 100% or 110%? How about in a new window, or a new private window? (You can use the right-click context menu for testing.)

Or is the setting lost the next time you exit Firefox and start it up again, back to 100%?

While the website is opened, any new opening for the website either as new tab or new window, it opened as the website is viewed (110%)

The problem happens when start the website from the beginning, where it is not running on a window nor on tab (For example when the Windows system just restarted)

Hi AliAlomran, sometimes users have cleaning software that removes some browser data at Windows startup (example would be CCleaner). If you have any programs like that, could you set them not to touch Firefox data?