I created a small site for searching in Firefox common phrases, and I noticed that while that was on local disk, i.e., loaded from file://, I couldn't search for "file", and now that it's up on http://l10n.mozilla.org/~axel/glossary/, I can't search for "http".

Just tried, and I couldn't search for http://l, either, http://w did promptly give an empty result.

Reproduced this on http://people.mozilla.com/~faaborg/files/granParadisoUI/icons/iconInventory.html, too.

Tested on Firefox 2 and current trunk builds, and on Safari 2.0.4.