For years now my htaccess has been referring requests to missing pages to an error page using an absolute url
ErrorDocument 404 http://www.mywebsite.com/404.php
This had the effect of serving a 302 redirect pointing to the error page, which then issued the 404 header, for any requests to missing pages.
The other day I thought that redirecting the browser to the error page might not be the right way, and I realised that by using the path from the server root eg
ErrorDocument 404 /404.php
the server would issue a 404 header, while keeping and keep the url as it is.
Eg I request www.mywebsite.com/missing_page.html and the server issues a 404 header, serves the page /404.php, and keeps the url as it is.
I thought this was the right way to go, and seems to be what other sites are doing.
However, this morning I noticed some of my pages dropping severely in the google serps. Is it at all possible that this change in serving error pages has given google the idea that there’s something shady about my site or pages?