Is it a problem to use a 301 redirect to a 404 error page, instead of serving directly a 404 page?

[lcourse]

We are building URLs dynamically with apache rewrite.
When we detect that an URL is matching some valid patterns, we serve a script which then may detect that the combination of parameters in the URL does not exist. If this happens we produce a 301 redirect to another URL which serves a 404 error page,

So my doubt is the following: Do I have to worry about not serving directly an 404, but redirecting (301) to a 404 page? Will this lead to the erroneous original URL staying longer in the google index than if I would serve directly a 404?

Some context. It is a site with about 200.000 web pages and we have currently 90.000 404 errors reported in webmaster tools (even though only 600 detected last month).

[SilverDoor]

Hi,

You should never redirect to a 404 page.

Search Engines are going to see this as an error and may even think you are trying to manipulate users around your site.

I would redirect the pages to a relevant page on your site.

With regards to the huge number of errors now appearing, I need some more details to answer the question:

• How many 404's would you expect there to be (give an estimate)?
• How many 301 redirects do you think would have been implemented with the script?
• Have you recently changed anything else with the HTTP Status Codes?

SilverDoor

[lcourse]

thanks a lot SilverDoor.

The huge number of errors, were caused by a problem with the internal site architecture several months ago which got thousdands of pages in the index that should not exist (and also have no other related relevanted pages). This architecture is fixed now. Still for some reason mobile crawler of webmaster tools is returning now suddenly lots of 404 for mobile view, which I suspect are coming from old 404 in google cache.

[SilverDoor]

I suspect you may be right.

How long ago did they appear?

Are they starting to go gradually down or up?

[lcourse]

in webmaster tools 404 are going gradually down for desktop and now suddenly going up for mobile for pages that are not linked to for months.