Short answer is: use Unicode UTF, preferably UTF-8. You did not explain how exactly did you screw up things; please see my comment to the question.
Don't leave anything to defaults (say, browser defaults). In each file, explicitly speciagefy Content-Type with charset. Your head element needs to include something like
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
Why it should be not just HTTP header, but HTML
http-equiv
? By many good reasons. One important reason is this: of the user saves the page into a local file, HTTP headers won't be preserved.
Of course, actual content encoding should match it. :-)
—SA