I've been working for many months on editing "MSSQL" out of question titles and replacing it with "SQL Server". I've been using the search
http://stackoverflow.com/search?q=intitle%3A1+mssql, which returns four pages of results (down from five, I'm proud to say).
However, when I click the "Newest" tab, I get a page full of results, and then the page displays again with only a few results (four the first time I did it today, now three).
I've never seen such behavior from the search results before.
This may be related to the page size calculation. I switched to using the "Active" tab, and noticed that it also did not show a full screen (50) of questions. However, it did show the pager at the bottom of the screen, and paging to the "Next" page worked.
Also, switching to 30 questions per page showed an empty screen!
The fact that I get a full page when using the "Relevance" tab fooled me into not trying the following simple experiment: turn off "hide ignored tags".
Doing that showed that the entire first page of search results were in hidden tags. I believe it is well-known (or at least, "known") that the paging algorithm first fills up a page, then removes questions in hidden tags, if you have "hide ignored" set. Since the first page has nothing but ignored tags, the entire page was empty.
I didn't even bother to look at the bottom of the page for the pager, since it looked like the page was empty!
I still don't understand why none of the tabs shows more than four pages of results whether or not I'm hiding tags, but that's a different question.