What is the web page you are having problems with?

https://support.mozilla.org/en-US/kb/websites-look-wrong-or-appear-differently

https://support.mozilla.org/en-US/kb/firefox-slow-how-make-it-faster

https://support.mozilla.org/en-US/kb/firefox-uses-too-many-cpu-resources-how-fix

https://support.mozilla.org/en-US/kb/firefox-hangs-or-not-responding

https://support.mozilla.org/kb/Firefox+is+already+running+but+is+not+responding

Separate Security Issue: Update your Adobe Reader Version 2015.016.20039 Note: Other Software is offered in the download.

Sorry. I'm hoping to avoid refreshing Firefox which is the only thing I haven't tried. BTW, I've tried to update Adobe Reader, but it won't let me get to "Step 3". Instead, I get sent to a page (https://get.adobe.com/reader/completion/adm/?exitcode=-1&type=install&preinstalled=1) which asks me to join Creative Cloud Photography plan for $9.99 a month. The Join Now button is the only one there. There is no Step 3 or Finished button.

That page should come up after the player is installed.

Type about:addons<enter> in the address bar to open the Add-ons Manager. Hot key; <Control>(Mac=<Command>) <Shift> A)

On the left side of the page, select Plugins. Look for Shockwave Flash. What version is it?

Flash Player Test Page
YouTube Test Page: What video does this browser support

Thanks Fred. "Shockwave Flash 21.0 0.242" in big print at the top and "Shockwave Flash 21.0 r0" below that. "Last updated 17 May 2016". Flash Player: "You have version 21,0,0,242 installed" YouTube: "The HTML5 player is currently used when possible." I should add that in the Firefox Plugin Status page I'm told that I have Adobe Reader version 11.0.10 (verified in Get Info) and I get the warning to "Update Now" that the version is "vulnerable". I have tried to update it, but as I've said, I can't get to Step 3.

I will tell you how to manually remove those plugins. After, try installing them again.

Note: Windows users should download the active_x for Internet Explorer. and the plugin for Plugin-based browsers (like Firefox).

Note: Windows 8 and Windows 10 have built-in flash players and Adobe will cause a conflict. Install the plugin only. Not the active_x.

Flash Player Version: 21.0.0.242 Flash Player (Linux) Version 11.2.202.621

https://get.adobe.com/flashplayer/ Direct link scans current system and browser Note: Other software is offered in the download.

https://get.adobe.com/flashplayer/otherversions/ Step 1: Select Operating System Step 2: Select A Version (Firefox, Win IE . . . .) Note: Other software is offered in the download.

Adobe PDF Plug-In For Firefox and Netscape: Adobe Reader Version 2015.016.20039 Note: Other Software is offered in the download.

Type about:plugins<enter> in the address bar. Now search for the plugin.

Example; Adobe Acrobat File: nppdf32.dll,nppdf32.dll Path: C:\Program Files (x86)\Adobe\Reader 11.0\Reader\browser\nppdf32.dll,C:\Program Files (x86)\Adobe\Reader 11.0\Reader\AIR\nppdf32.dll Version: 11.0.9.29 State: Enabled Adobe PDF Plug-In For Firefox and Netscape 11.0.9

This will show you the path to that program. Copy the Path Only. Also, note the name of the file, and remember it. Now Close Firefox. Open your file browser and paste the path in the address bar. Find the file, and delete it. Now you can restart Firefox. Warning ! Remember to delete the right program.

To be safe, remove all of them. Then install the current.

Sorry to take so long to reply. I did as you suggested and deleted the plugin that was a problem on the Plugin Status page.

Path: /Library/Internet Plug-Ins/AdobePDFViewerNPAPI.plugin File: AdobePDFViewerNPAPI.plugin

The message telling me to update it is finally gone. Thank you! Oddly when I did update it, I was told that I already have the newest version.

I've also used the Add-ons Manager to temporarily turn off each of the plugins and then turn them back on. That had no effect on the spinning pinwheel at NASA-TV which is where this all started.

Here are the Internet Plugins I currently have. According to Add-ons Manager and the Plugin Status page everything is okay:

AdobePDFViewer.plugin EPPEX Plugin.plugin Flash Player.plugin flashplayer.xpt Flip4Mac WMV Plugin.plugin JavaAppletPlugin.plugin nsIQTScriptablePlugin.xpt Quartz Composer.webplugin QuickTime Plugin.plugin SharePointBrowserPlugin.plugin SharePointWebKitPlugin.webplugin

Good.

Use this link to check that your plugins are up-to-date. If any are listed as unknown or research, do not worry about them.

Thanks. When I mention the Plugins Status page above, that's the page I've been referring to. That's where I was getting the message to update Adobe Reader, but that notice didn't disappear until I deleted the Adobe PDF Viewer NPAPI plugin following your instructions.

Hello,

I am glad to hear that your problem has been resolved. If you haven't already, please select the answer that solves the problem. This will help other users with similar problems find the solution more easily.

Thank you for contacting Mozilla Support.

When I tried NASA-TV this morning, I was still getting the spinning pinwheel. However, I just tried it again, and it came up exactly as it used to. Between the two tries, I did not do anything to the plugins. I contacted NASA last week, thinking that the problem might be at their end, but since I seem to be the only Firefox user who raised the issue here, I doubt that the problem was in Houston. Bottom line: I have NASA-TV again, but I don't know why. Thanks to FredMcD for his efforts

It could have been a corrupt file that was overwritten.