I get an alert message several (10+) times a day while browsing the web, it says that the URL is not valid and cannot be loaded. Sometimes I can hit OK on the message and then click the link again and it will load, other times I have to go through this process several times and others I have to restart FF to get the page to load. This happens on many of the sites I visit and is not limited to just a particular few. It also happens when I click bookmarks from the menu and bookmarks toolbar. Sometimes it even happens when I type in web addresses that I know are valid (ex: espn.com). It's been happening since I installed FF but it is getting worse.
It's possible that you are having a problem with some Firefox add-on that is hindering your Firefox's normal behavior. Have you tried disabling all add-ons (just to check), to see if Firefox goes back to normal?
Whenever you have a problem with Firefox, whatever it is, you should make sure it's not caused by one (or more than one) of your installed add-ons, be it an extension, a theme or a plugin. To do that easily and cleanly, run Firefox in safe mode (don't forget to select Disable all add-ons when you start safe mode). If the problem disappears, you know it's from an add-on. Disable them all in normal mode, and enable them one at a time until you find the source of the problem. See this article for information about troubleshooting extensions and themes and this one for plugins.
If you need support for one of your add-ons, you'll have to contact its author.
If the problem does not disappear when all add-ons are disabled, please tell me, so we can work from there. Please have no fear of following my instructions to the line, as all can be easily undone.
I suspect that the internet is doomed by an untenable bureaucracy that will continue to plague users forever, until it implodes on itself. Just like government. I suggest in the future you test more and update less, as I am now forced to abandon the use of firefox temporarily, until the issue is resolved. By the way clearing cache does not work, starting in safe mode does not work, updating plugins does not work, for the message: "the url is not valid and cannot be loaded". For the record the url is valid it has been online for 3 years. Thank God the visitors of my site are not likely to use firefox as their default browser. Switching to Chrome NOW!
interesting that 8 people found your reply not helpful, but none of these people have a solution that will actually let firefox load a simple web page. I have this problem too. Firefox is now a virtual paperweight.
In other news, I made a forum post last night about this issue, with much more specific troubleshooting information... and now I can't find it, anywhere... My forum settings have "Watch forum threads I start:" checked... so... where in this interface would I go to watch stuff? Wow, either Firefox & associated forums is some of the best software since sliced bread and I'm a complete idiot, or...
from what i can tell it has to do with SSL or TLS encryption, when i disable them i can navigate around to a few sites that gave me the error without getting the error. unfortunately, lots of sites require SSL - like GOOGLE.com
this is really awful, i think that the ssl encryption uses proprietary URLs and firefox doesn't know what to do with them.
mozilla, fix it or give us an option to DL Firefox 8.
if you want to use firefox in the meantime, download http://www.oldversion.com/download-Mozilla-Firefox
it STILL has an error with certificates however(the other major error people are experiencing with the new doomsday y2k throwback machine known as firefox 9), so good luck.
I've noticed that I get the error message, "The URL is not valid and cannot be loaded," any time I open a new window, whether it's a tab or a separate window, including when I first turn Firefox on. It doesn't seem to have any relevance to web pages, only new windows.
I think it started after I clicked on the "do not show" link in the Blekko page that was opening whenever I opened a new tab.
Thank you, and I hope this helps with finding a solution.
Start Firefox in Troubleshoot Firefox issues using Safe Mode to check if one of the extensions or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance/Themes).