400 errors occurred after submitting the application information for background editing of zblog Bad Request cannot be accessed

The Apache server manages and edits the application information in the background theme of the zblog website. After submission, 400 errors occur and the website cannot be accessed. The prompt is as follows:

Bad Request

Your browser sent a request that this server could not understand.
Size of a request header field exceeds server limit.

It roughly means: The browser sent a request that the server could not understand. The size of the request header field exceeded the server's limit.

At first glance, I thought that there was a problem with the theme code. Then I changed another zblog website under the same server to the default theme for the same operation. The same problem also occurred. This can eliminate the theme problem. Is it the problem of the Z-Blog program itself? It seems unlikely, so I searched the Internet and found a reason that I agree with: there are too many cookies.

Clear the cookie and cache of the browser later. The problem is solved.

How to clear cache and cookies in Firefox browser:

1. In the browser toolbar, select "Tools - Settings", then select "Privacy and Security", and find "Cookies and website data":

2. Click the "Clear Data... (L)" button, and check "Cookie and Website Data" and "Cached Network Data" in the pop-up box:

Then click the "Clear (L)" button and restart the browser to restore the website access.

PS： In theory, only delete cookies.

If you don't understand the method of clearing cache and cookies in other browsers, you can search relevant tutorials on the Internet.