If you use extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) that can block (wanted) content (e.g. Adblock Plus, NoScript, Ghostery, uBlock Origin) always make sure such extensions do not block (wanted) content.

• make sure that your extensions and filters are updated to the latest version

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You can reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files.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 the cookies from websites that cause problems via the "3-bar" Firefox menu button (Options/Preferences).

"Clear the cache":

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

"Remove the cookies" from websites that cause problems.

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

Start Firefox in Safe Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration is causing the problem.

• switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Appearance
• do NOT click the "Refresh Firefox" button on the Safe Mode start window

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

"Remove the cookies" from websites that cause problems.

How would I know which websites cause problems so as to remove those cookies?

You can inspect cookies and passwords and permissions for the domain in the currently selected tab via these steps:

*click the Control Center 'i' icon at the left end of the location/address bar

• click the arrow to expand the security message
• click "More Information" to open "Tools -> Page Info"
• click "Permissions" to inspect and modify permissions
• click "Security" to inspect and modify cookies and passwords in a standalone window

You can also use the Storage Inspector to check all types of storage (cookies and local storage). You can remove specific items via the right-click context menu.

• "3-bar" menu button or Tools -> Web Developer
• https://developer.mozilla.org/Tools/Storage_Inspector

But how would I know which ones are causing trouble? Deleting all cookies seems counterproductive, since most of them serve a helpful purpose.

Just remove the cookies for the site you're visiting. Yes, you'll have to log in again, but all the critical information should be on the server. If the bar is generated by a script from a related site (e.g., something containing blogger, blogspot, etc.) then you can clear cookies for those sites as well.

As a quick test, you could try visiting the page using a private window (assuming you aren't using ALL private windows). Private windows do not share the same cookie jar as regular windows, so bad old cookies should not be a factor in how the site works in a private window.

More info:

• Private Browsing - Use Firefox without saving history
• Beware of blocked content if you see a shield icon at the left end if the address bar: What happened to Tracking Protection?

Thanks. Removing cookies did not change the problem.

Do you use any add-ons or custom style rules that affect fixed-position headers (i.e., force them to scroll up)? If so, they would have been disabled in the Safe Mode test. Did it make any difference to visit the site in Firefox's Safe Mode?

To try to determine whether it's some setting/permission we're not thinking of, or a different kind of problem, you could try:

New Profile Test

This takes about 3 minutes, plus the time to test your blog.

Inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it.

Click the Create a New Profile button, then click Next. Assign a name like July2017, ignore the option to relocate the profile folder, and click the Finish button.

After creating the profile, scroll down to it and click the Set as default profile button below that profile, then scroll back up and click the Restart normally button. (There are some other buttons, but I think those are still "under construction" so please ignore them.)

Firefox should exit and then start up using the new profile, which will just look brand new.

Does your blog work any better in the new profile?

When you are done with the experiment, open the about:profiles page again, click the Set as default profile button for your normal profile, then click the Restart normally button to get back to it.

Okay, we're not there yet, but now we're making soem progress. Yes, the header does show when using the new profile. Of course nothing else does, so I had to get back to my original profile to make anything else work, like bookmarks and my ability to connect to this help system, but we do know that the header does not show up with my current profile and it does show up with the new, blank profile. I suspect that tells you more than it does me, so I'm sitting with bated breath ready for the next step.

I am, by the way, pleasantly impressed with the number of folks who are offering help here. Nice group.

Firefox refresh under "troubleshooting" solved the problem. I had to restore all of the settings for the title bar and home page, but bookmarks remained intact and so did things like passwords.