This can be caused by corrupted cookies.

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"

The layout of the Options page has changed a lot starting in Firefox 56. Currently, the easiest way to clear the cache and selected cookies might be:

Open the Options/Preferences page:

• 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 search box at the top of the page, type cache and Firefox should filter to a small set of controls.

Cache

Click the Clear Data button and Firefox should display a small dialog with two choices. Uncheck Cookies and Site Data since that would be too much to clear, but keep Cached Web Content selected. Then click "Clear". This may take a while if you have a large hard drive.

Site Cookies and Data

Click the Manage Data button and Firefox should display a list of sites that have stored cookies or other data. You can highlight selected sites and remove cookies for the affected (sites), then click Save Changes.

Any improvement?

trnmn12 said

I try to go to a website and a error code 400 prevents me from opening it

How to Fix a 400 Bad Request Error

~Pj