Last modified: 2011-04-14 15:13:23 UTC
Some wikis like to put helpful forms in their MediaWiki:Noarticletext to assist in article creation, searching, and the like. And the vast majority of wikis have a search box on every page. However, with 404s being served almost everywhere Noarticletext is shown (and possibly due to the must-revalidate and zero's maxage headers), these pages are uncacheable in certain browsers (at least some /most Mozilla derivatives), so entering information into these forms, submitting, and then clicking 'back' results in a complete page re-fetch and erasure of any form inforation. There may be no way to solve this without removing the 404 status codes.
Note that the same erasure issue exists with special pages, or if the page you've searched from has been changed before you click "back".