In a post on Google+, Google’s Gary Illys said that it’s usually not advisable to use 403 error codes if your server has a problem:
“The different HTTP status codes in the error ranges (4xx and 5xx) are treated differently on our side. For example, a 403, 404 or 410 status code will cause us to drop the page from our index pretty fast, because the users won’t get anything either.
On the other hand if a page comes back with a 503 status code, we will keep the page indexed for some time because a 503 means temporary server issues and it may very well happen that users will be able to access the page.
Please keep this in mind when you are deciding what status codes to return in different situations. We’ve seen huge sites lose load of their pages from our index because they were serving them with a 403 status code instead of a 503.”
Make sure that your web pages use the correct HTTP codes. You can do this with the website audit tool in SEOprofiler. If you haven’t done it yet, create your SEOprofiler account now and check your website with the audit tool: