[mothered]

Why I ask you that question right. So other people can understand that term.

It's not difficult to Identify It's meaning.

Enter "WAF" In Google, and there's pages of search results.

right, but there are some lazy people out there that do not want to do a simple google search.

It can be either client-side or server-side.

For Instance, In terms of client-side, you could be trying to access a cache version of the web page and It'll throw a 403 error. There's too many causes to mention server-side.