An alternative is using server side includes inside a table for navigation bars - A 1 row 2 column table with the left column using a SSI navigation page and the right column the page content. On the issue of linking to external sites, frames allow one to link external content within a frame of your own page. If linking external web sites inside a frame, have the link open up in a new window or on top of the current page. Make sure your java code complies with Java 1.02, the version of java that older java interpreters use. Keep in mind that java applets must be interpreted after downloading, so keep applets small.
Some web sites use a high and low bandwidth version.
While providing two versions of a web site is an alternative, it requires more work. Keep your file sizes as small as possible. Optimize graphics when possible with software like Fireworks, ImageReady, or Debabelizer. Optimize multimedia files with software like Debabelizer and Media Cleaner. With 5 versions of Microsoft Internet Explorer and 5 versions of Netscape Navigator, there are many incompatibilities between all the versions.