What special characters are supported in HTML (copyright, accents, etc.)?
It is best to use HTML "entities" whenever possible,
such as < for the less-than symbol and © for the
copyright symbol. Unfortunately, support for these is not quite
universally consistent among browsers. Keep in mind that text-based
browsers naturally can't display characters not present in the font
being used. When in doubt, spell out "copyright."
Consider the following list of resources provided by Mark S. Zinzow.
If possible, use entities in preference to transparent GIFs, which
take far more time to deliver to the user. (Slow pages mean
frustrated customers...)
World Wide Web FAQ