Gainesville's Civic Media Center, a nonprofit, nongovernmental library for the public, is really careful about HTML compatibility:

"The CMC web page uses text inside tables. This may cause problems for users of Netscape Navigator for Mac version 1.1 or earlier, and for users of versions of NCSA Mosaic for Windows prior to 2.0 alpha 8. You may wish to update your browsing capabilities with new software."