A menu item (File->Save As), which is a part of
Wang's patent from 1984 on "Video Text Systems". At 1999, they've (a
Microsoft-ally at that point) has claimed
Netscape's infringment of the patent in
Netscape Navigator software. At the same opportunity, Netscape was also sued for the
Bookmarks concept and
Saving files with file extensions and then retrieving the pages and decoding the files based on the file extension. The lawsuit was later dismissed, as the court found that patents, which were filled for
Teletext systems, didn't apply to
computers.
Read more at http://www.mozilla.org/legal/wangsuit.html