At least in Firefox the search pane has a ‘Match Diacritics’ option. Turning it on causes it to match only the precise characters in the textbox. (It’s slightly misnamed, since it doesn’t just handle diacritics, but also cases like ⟨e⟩ vs ⟨ɛ⟩.)

The wonders of Unicode collation folding: http://www.unicode.org/reports/tr10/#Collation_Folding