this is what I get regardless of where I go: Your connection is not secure

The owner of www.yahoo.com has configured their website improperly. To protect your information from being stolen, Firefox has not connected to this website.

Learn more…

Report errors like this to help Mozilla identify and block malicious sites

That is a self-signed certificate:

Subject 	CN=support.mozilla.org
Issuer 	CN=support.mozilla.org
Valid From 	Sept. 1, 2016, 12:58 p.m.
Valid To 	Sept. 1, 2022, 12:58 p.m.

It doesn't show who really issued the certificate.

Are you using a proxy or VPN?

You can check the connection settings.

• Options/Preferences -> Advanced -> Network: Connection -> Settings
• https://support.mozilla.org/en-US/kb/Options+window+-+Advanced+panel

If you do not need to use a proxy to connect to internet then try to select "No Proxy" if "Use the system proxy settings" or one of the others do not work properly.

See "Firefox connection settings":

• https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can

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

Boot the computer in Windows Safe mode with network support to see if that has effect in case security software is causing problems.

• http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/
• http://www.7tutorials.com/4-ways-boot-safe-mode-windows-10

Do a malware check with several malware scanning programs on the Windows computer.

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware

Please scan with all programs because each program detects different malware. All these programs have free versions.

Make sure you update each program to get the latest version of their databases before doing a scan.

• Malwarebytes' Anti-Malware:
  http://www.malwarebytes.org/mbam.php
• AdwCleaner:
  http://www.bleepingcomputer.com/download/adwcleaner/
  http://www.softpedia.com/get/Antivirus/Removal-Tools/AdwCleaner.shtml
• SuperAntispyware:
  http://www.superantispyware.com/
• Microsoft Safety Scanner:
  http://www.microsoft.com/security/scanner/en-us/default.aspx
• Windows Defender:
  http://windows.microsoft.com/en-us/windows/using-defender
• Spybot Search & Destroy:
  http://www.safer-networking.org/en/index.html
• Kasperky Free Security Scan:
  http://www.kaspersky.com/security-scan

You can also do a check for a rootkit infection with TDSSKiller.

• Anti-rootkit utility TDSSKiller:
  http://support.kaspersky.com/5350?el=88446

See also:

• "Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked

this is what I just got when I went to

https://support.mozilla.org/en-US/kb/Options+window+-+Advanced+panel

support.mozilla.org uses an invalid security certificate. The certificate is not trusted because the issuer certificate is unknown. The server might not be sending the appropriate intermediate certificates. An additional root certificate may need to be imported. Error code: SEC_ERROR_UNKNOWN_ISSUER

s/n#4C:87:D7:6E:20:6D:0C:8F:48:30:00:BF:53:9F:B2:0B

SHA-256 finger print 54:7B:54:50:DD:FD:D9:3A:D8:56:BB:20:94:70:63:55:02:F5:2E:2A:B9:5D:86:B7:A7:EC:0D:1A:E0:5C:13:C9 SHA1 53:A9:01:AB:BB:CA:3F:44:86:AE:68:61:D7:FA:81:CA:BE:3F:32:3F

This is what I get when I add exception :

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mozilla support

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Please wait... Advanced panel - Accessibility, browsing, network, updates, and other advanced settings in Firefox (Redirected from Options window - Advanced panel) Note: This article applies to Firefox version 55 and below. Firefox OptionsPreferences have been reorganized starting in version 56.

This article explains the settings available in the Advanced panel of the Firefox OptionsPreferences page. These are settings that aren't used very often, such as proxy settings and various other advanced settings that only some people need. Table of Contents

   1 General tab
       1.1 Accessibility
       1.2 Browsing
   2 Data Choices tab
   3 Network tab
       3.1 Connection
       3.2 Connection Settings Dialog
       3.3 Cached Web Content
       3.4 Offline Web Content and User Data
   4 Update tab
       4.1 Firefox updates
       4.2 Automatically update
       4.3 Firefox updates
       4.4 Automatically update
   5 Certificates tab

General tab

Fx54AdvancedPanel-GeneralTab Fx55AdvancedPanel-GeneralTab Accessibility

   Always use the cursor keys to navigate within pages: When this setting is enabled, Firefox will display a movable cursor in web pages, allowing you to select text with the keyboard. This mode is known as Caret Browsing and you can toggle this mode by pressing F7. 

   Search for text when you start typing: When this setting is enabled, Firefox will find within the current web page what you type as you type it. While you are finding typed text in the page, the Find Toolbar will automatically display at the bottom of the window to show information about what you've found. 

   Warn you when websites try to redirect or reload the page: When this setting is enabled, Firefox will prevent websites from redirecting you to another page, or automatically reloading. 

Browsing

   Use autoscrolling: Autoscrolling is a useful feature which allows you to scroll the page by clicking the middle mouse button (usually the scroll wheel) and moving the mouse up or down. Some people find this annoying, so autoscrolling can be disabled with this setting. 

   Use smooth scrolling: Smooth scrolling can be very useful if you read a lot of long pages. Normally, when you press Page Down, the view jumps directly down one page. With smooth scrolling, it slides down smoothly, so you can see how much it scrolls. This makes it easier to resume reading from where you were before. 

   Use hardware acceleration when available: Firefox can use your computer's graphics processor to display some pages with video and animation. This makes Firefox faster since your computer's graphics processor is much better than your computer's main processor at displaying these types of things. This box is checked by default but the feature isn't available for all graphics processors. Firefox will enable it when possible. Read more about hardware acceleration.
   If you change this setting you must restart Firefox.
   To restart Firefox:
       Click the menu button New Fx Menu and then click ExitQuit Close 29 .
       Start Firefox the way you normally do. 

   Check your spelling as you type: When this setting is enabled, Firefox will check your spelling and offer possible corrections as you type in web forms. Note that you may need to download a dictionary; to do so, right-clickpress Ctrl and click on any text field, enable spellchecking if necessary, and then use the provided Languages menu to download a dictionary. 

Data Choices tab

Fx38AdvancedPanel-DataChoices Fx51Advanced-DataChoices

   Enable Firefox Health Report: The Firefox Health Report (learn more) provides you with information about your browser’s performance and stability over time. This setting is enabled by default. Mozilla uses this data to provide you with meaningful comparisons and tips. Mozilla also aggregates the data that everyone shares to help improve Firefox. 

       Share additional data (i.e., Telemetry): Also enabling this setting will send anonymous data (learn more) to Mozilla about the real world performance of Firefox. This information will be used to make Firefox better. 

   Enable Crash Reporter: If Firefox crashes, the Mozilla Crash Reporter will appear, asking you if you want to report the crash to Mozilla. When this setting is enabled, the Tell Mozilla about this crash so they can fix it check box in the Mozilla Crash Reporter window will be checkmarked by default. 

   Allow Firefox to send backlogged crash reports on your behalf: If Firefox crashes, the Mozilla Crash Reporter will appear so that you can tell Mozilla about the crash. In some cases, there may be reports for earlier crashes that were never submitted. When you enable this setting, Firefox will automatically send those backlogged reports to Mozilla. 

Network tab

Fx38AdvancedPanel-Network Connection

Your organization or Internet service provider may offer or require you to use a proxy. A proxy acts as an intermediary between your computer and the Internet. It intercepts all requests to the Internet to see if it can fulfill the request using its cache. Proxies are used to improve performance, filter requests, and hide your computer from the Internet to improve security. Proxies are often part of corporate firewalls. Connection Settings Dialog

   No proxy: Choose this if you don't want to use a proxy.
   Auto-detect proxy settings for this network: Choose this if you want Firefox to automatically detect the proxy settings for your network.
   Use system proxy settings: Choose this if you want to use the proxy settings configured for your operating system.
       This is the default setting. 
   Manual proxy configuration: Choose this if you have a list of one or more proxy servers. Ask your system administrator for the configuration information. Each proxy requires a hostname and a port number.
       If the same proxy name and port number are used for all protocols, check Use this proxy server for all protocols.
       No Proxy For: List of hostnames or IP addresses that will not be proxied. Use <local> to bypass proxying for all hostnames which do not contain periods. 
   Automatic proxy configuration URL: Choose this if you have a proxy configuration (.pac) file. Enter the URL and click okay to save changes and load the proxy configuration.
       Reload: The reload button will load the currently available proxy configuration. 

Cached Web Content

Pages you view are normally stored in a special cache folder for quicker viewing the next time you visit the same page. You can specify the amount of disk space the cache can use here. You can also immediately clear the contents of the cache.

   Clear Now: Immediately clears the current contents of the cache, freeing the disk space used by the cache.
   Override automatic cache management: Checking this box allows you to specify the maximum size, in megabytes, of the cache on your computer. 

Offline Web Content and User Data

   Clear Now: Immediately clears data that is being saved by websites for use when you are offline.
   Tell me when a website asks to store data for offline use: Allows websites to store data necessary to be used without an internet connection. If you have previously blocked a website from storing data for offline use and changed your mind, you can click the Exceptions… button. Select the site you want to stop blocking, and click Remove. To remove all websites in the list, click Remove All Sites. 

Update tab

Fx38WinAdvancedPanel-Update Fx38MacLinuxAdvancedPanel-Update

Fx49AdvancedPanelUpdate-win7 Fx49AdvancedPanelUpdate-MacLinux

sddrlj said

this is what I get regardless of where I go: Your connection is not secure The owner of www.yahoo.com has configured their website improperly. To protect your information from being stolen, Firefox has not connected to this website. Learn more… Report errors like this to help Mozilla identify and block malicious sites

found and ran a compatibility program and firefox now works. found it by right clicking on browser icon -right click on firefox name - then properties - then compatibility -then run compatibility test. this fixed it. MY VERY GRATEFUL THANKS FOR ALL THE HELP AND ENCOURAGEMENT I WOULD NOT HAVE FIGURED IT OUT WITHOUT YOU!! Once again Thank You