As I shift many URL's on my site from non-friendly to friendly, I came across an old URL that was used for testing that google later ended up scanning but now I no longer use the URL. Its in the unfriendly form like this:http://example.com/something.php?something=something&In the past, that URL matched another on my site and in order to rectify it, I had to change the status code (and make the URL not return an actual webpage). At first I thought using the code 410 to indicate gone to google, but now I figured http status 400 is better because all my other clean URLs never contain an & in them and http status 400 stands for malformed request.Is this an acceptable practice? or should I just convert it to http status 410? What would search engines think of this practice? (I'm just trying to follow standards here)
Can an HTTP status 400 be a substitute for a 410?
url;http;410 gone;http code 400
Why 410 gone?Since the page once existed the correct header status return would be 410 gone, this will inform Google and other search engines to drop the page from its index. You should avoid using status 400 bad request  since this implies the server did not understand the request due to malformed syntax. Using undesirable status codes will populate your error logs and can make fault finding harder on actual issues.What about 404?Using either a 404 or 410 statuses is considered ok, however if you know the page is never coming back then its best to use a 410 gone. Google has said that they treat the outcome of 404 and 410 the same but the 410 is dropped quicker due to the fact that 404s can occur when its not intended. 