Is it true or is there any known case you've heard about : "Google likes better if you answer back 200.... and a 304 may get you in problems..."? I'd appreciate any help you guys may provide!
Nicky, neither of the two status codes will be a problem. The "200" indicates that the request succeeded. "304" indicates that the file has not changed since the crawler's last visit, and there is no need to download it again. I just checked my traffic logs and see that no file is sent with a 304 status code. http://www.iaps.com/gifs/perm/no-file-sent-with-304.png If you change contents of the web page, the next time Googlebot comes around you will see a 200. After that, you will again see a 304. On the other hand, Google does not like to see a 302, but let's leave that discussion for another thread...
whittier, I see your point. You know, I have no doubts about how Http 1.0 / 1.1 works Still, my concern right now is if we are in fact going to loose indexation the moment we decide to reply with 304 and start using if-modified-since !! Have you ever heard any case like it?
A single 304 does not lead to removal from the index. If your material has not been updated for months or years, your rankings will drop as more relevant/useful material becomes available. I view a 304 as something positive. It is telling the SE that it was successful getting the file in the past and nothing has changed. Items are removed from the SE index when they are no longer available/accessible (401,403, 404, etc.) or they are found to be duplicate content (not the original). I would be on the lookout for unsuccessful attempts to crawl your site. Sign up for Google's Webmaster Tools. The data they provide is invaluable.
Here is a direct quote from Google's Webmaster Guidelines: "Make sure your web server supports the If-Modified-Since HTTP header. This feature allows your web server to tell Google whether your content has changed since we last crawled your site. Supporting this feature saves you bandwidth and overhead."