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. Changing browser's encoding is usually done from its View Menu.
If you see squares or question marks instead of the symbol you need to make sure you have the language pack installed necessary to show the symbols.
Installing Windows XP Language Packs:
(depending on the version of XP you have, you may need to insert your WINDOWS XP SETUP CD) then go to Control Panel >> Add/Remove Programs >> Windows Components scroll down in the list and put a checkmark next to “language packs”. If you cant find that, then go here instead Control Panel >> Regional and Language Options >> Languages then made sure both boxes under Supplemental Language Support are checked. Click NEXT and then let it do its thing. You will probably then have to reboot.
Enabling International Support in Windows XP/Server 2003 Family: http://www.microsoft.com/globaldev/handson/user/xpintlsupp.mspx
How to Configure Regional and Language Support for User Accounts: https://www.microsoft.com/windowsxp/using/setup/expert/reginalsup.mspx
Vista:
Install a display language: http://windowshelp.microsoft.com/Windows/en-US/help/4a90fe71-cca6-4965-ab39-97f92ca1a03f1033.mspx
Windows Vista Ultimate language pack release information: http://support.microsoft.com/kb/925471
Installing Language Interface Packs: http://technet.microsoft.com/en-us/library/cc766278(WS.10).aspx
Win 7 Language pack:
How to easily download and install Windows 7 Language Packs (MUI packs): http://windows7center.com/tutorials/how-to-download-and-install-windows-7-beta-language-packs-mui-packs/
Windows 7 RTM Language Packs now available via Windows Update: http://windows7center.com/news/windows-7-rtm-language-packs-now-available-via-windows-update/
How do I get additional language files?: http://windows.microsoft.com/en-US/windows-vista/How-do-I-get-additional-language-files
Ron