Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

• Do NOT click the Reset button on the Safe Mode start window.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Clear the cache and cookies only from websites that cause problems.

"Clear the Cache":

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

"Remove Cookies" from sites causing problems:

• Firefox/Tools > Options > Privacy > Cookies: "Show Cookies"

cor-el: Your suggestions did not solve the problem. The problem appears when I use:

  Firefox/Tools/Add-ons Manager/Extensions/Norton Toolbar 2014.6.2.3

I don't have this problem on a similar computer, running the same OS (Windows 7 Pro 64-bit) and Firefox 26.0 The only difference between the 2 machines is that I'm running Norton Internet Security, which I bought last summer and Norton Internet Security, which I bought in November. On both machines the Norton software is up to date using Live-Update. Here's the difference: On the machine without the problem Norton Toolbar 2013.4.5.2 is used. The the problem occurs on the machine using Norton Toolbar 2014.6.2.3.

I want to use Norton Toolbar as it adds to the safety of my browsing.

Some security software and add-ons have a "home page protection" feature (or "surfing protection" or "browser protection") that can block you from saving changes, or will override your changes. Check to see whether your newer Norton toolbar has this feature and turn it off temporarily so you can save the home page address correctly.

Note that Firefox comes with some built-in protection.

• https://support.mozilla.org/kb/how-does-phishing-and-malware-protection-work

jscher2000,

My Norton product does not have home page protection. In fact I have no problem setting a new home page with one exception. That exception is: http://forecast.weather.gov/MapClick.php?CityName=Houston&state=TX&site=HGX&textField1=29.7687&textField2=-95.3867&e=1 Initially I can change to this home page successfully, but if I log out and back into Firefox, I get the message in my first posting, i.e. "The requested URL /mapclick.php was not found on this server"

I have no problem permanently setting as my home page: http://www.weather.gov/forecastmaps From the latter URL I can then successfully transfer to the desired page but it is a 2-step process.

Am I correct in assuming that the Add-on Extension Norton Toolbar is developed by Firefox? If so, what is the difference between 2014.6.2.3, which does not work and 2013.4.5.2, which does work?

cor-el:

It is not a phishing or malware-protection problem. In addition to daily full-system scans with Norton, I also do daily full-system scans with Malwarebytes.

Please notice that the site giving the problem is a "gov" domain site: http://forecast.weather.gov/MapClick.php?CityName=Houston&state=TX&site=HGX&textField1=29.7687&textField2=-95.3867&e=1

I have used this site for years as my home page on Windows XP machines, Windows 7 Home Premium machines, and Windows 7 Pro machines. The problem first appeared when I switched to Firefox 26.0 and Add-on Extension Norton Toolbar 2014.6.2.3.

I have no problem permanently setting as my home page: http://www.weather.gov/forecastmaps

Am I correct in assuming that the Add-on Extension "Norton Toolbar" is developed by Firefox? If so, what is the difference between 2014.6.2.3, which does not work and 2013.4.5.2, which does work?

This is not a problem with home page protection, but with software that checks the prefs.js file and apparently changes links to lowercase versions.

Does this change only happen after restarting or possibly rebooting the computer or also during the current session?

You can try to make a backup copy of the prefs.js file and compare it against changes after rebooting the computer.

You can use this button to go to the Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)

Note that Windows hides some file extensions by default.
Among them are .html and .ini and .js and .txt, so you may only see the name without file extension.
You can see the real file type (file extension) in the Properties of the file via the right-click context menu in Windows Explorer.

Hi firefoxfandango, the Norton toolbars are supplied with your Norton software. Norton adds them to Firefox by listing them in a place checked by Firefox in the Windows registry.

Turns out this occurs in IE as well as Firefox, and Norton support said in November it is "tracking it". See: IE homepage URL changes uppercase letters to lowercase when closing - Norton Community.

Not sure what else to say...