Do you get that error if you access the site or if you click a link to got to another page?

You can reload the page and bypass the cache with:

• Press and hold Shift and left-click the Reload button.
• Press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)
• Press "Cmd + Shift + R" (MAC)

See Keyboard shortcuts - Perform common Firefox tasks quickly and Use mouse shortcuts to perform common tasks in Firefox

• "Clear the Cache": Tools > Options > Advanced > Network > Offline Storage (Cache): "Clear Now"
• "Remove the Cookies" from sites that cause problems: Tools > Options > Privacy > Cookies: "Show Cookies"

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of your add-ons is causing your problem (switch to the DEFAULT theme: Tools > Add-ons > Themes).

• Don't make any changes on the Safe mode start window.

See Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems and Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems

Error occur both ways.

Same error result in Safe Mode

No idea why or how, but I started getting a 501 error for my website. Now, the only way I can get firefox to load the site is if i type www.worklabs.ca. In every other browser, worklabs.ca works just fine.

i've cleared and reinstalled and restarted up the yin yang. Could this be a mod_security issue or some other server-related thing?

same issue here, multiple sites, always only in FF. Clearing cache does nothing.

This HAS to be a FF issue, not server-side; otherwise why does every other browser have no problems on the same sites?

Error in standard mode, but the site is accessed OK in Private Browsing mode.

@rfowler_chatnooga

Please start a new thread for your problem or question and provide troubleshooting information like your operating system and installed extensions and installed plugins.

• [start a new thread]
• [/kb/Using+the+Troubleshooting+Informatio...]

[Locking thread due to age]

Clear the cache and the cookies from sites that cause problems.

"Clear the Cache":

• Tools > Options > Advanced > Network > Offline Storage (Cache): "Clear Now"

"Remove Cookies" from sites causing problems:

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