Some symbols may not show because your computer does not contain the font set and/or your browser is not set to the correct Character Encoding (utf-8 is good). Changing browser's encoding is usually done from its View Menu. Unicode browser display test: http://home.tiscali.nl/t876506/entitiesTips.html
Maybe a problem too...
If you see squares or question marks instead of the language symbol(s) you need to make sure you have the language pack installed necessary to show the symbols. Be sure to set the language attribute and the direction the language is read:
Why should I use the language attribute in web pages? - http://www.w3.org/International/questions/qa-lang-why.en
Language information and text direction - http://www.w3.org/TR/html401/struct/dirlang.html
Would be nice if you gave link to page with problem.