"400 Bad Request"
"Bad Request. Your browser sent a request that this server could not understand."
"Bad Request - Invalid URL"
"HTTP Error 400 - Bad Request"
"Bad Request: Error 400"
"HTTP Error 400. The request hostname is invalid."
1. Check for errors in the URL. The most common reason for a 400 Bad Request error is because the URL was typed wrong or the link that was clicked on points to a URL with a specific kind of mistake in it, like a syntax problem.
2. Clear your browser's cookies, especially if you're getting a Bad Request error with a Google service. Many sites report a 400 error when a cookie it's reading is corrupt or too old.
3. Clear your DNS cache, which should fix the 400 Bad Request error if it's being caused by outdated DNS records that your computer is storing. Do this in Windows by executing ipconfig /flushdns from a CMD or Command Prompt window.
4. Clear your browser's cache. A cached, but corrupt copy of the web page you're trying to access, but are getting the 400 error on, could be the root of the problem. Clearing your cache is unlikely the fix for the majority of 400 bad Request issues, but it's quick and easy, and so worth trying.
5. While this is not a common fix, try troubleshooting the problem as a 504 Gateway Timeout issue instead, even though the problem is being reported as a 400 Bad Request.
6. Contact the website directly that hosts the page.
7. If nothing above has worked, and you're sure the problem isn't with your computer, you're left with just checking back later.