This is the Bluefish HTML editor.

It has (among others) the following major features

  Customizable syntax highlighting based on Perl Compatible regular expressions,
  Multiple encodings support
  Wizards for startup, tables, frames, and others
  Dialogs for many HTML tags, with all their attributes
  User-customizable toolbar for quick access to often used functions
  A custom menu, specify your own tags or sets of code, and define your own dialogs
  Custom search and replace pattern support for the Custom menu
  Function reference browser, including reference files for PHP and HTML
  User customizable integration of many programs, including weblint, tidy, make

Installation:
  See INSTALL file for information on how to install Bluefish
  
Starting Bluefish:
  run from the command line: bluefish
  run bluefish -h for more startup options

More information:
  See the manual in the doc/ subdirectory

Written by:
  see AUTHORS for more information

Reporting Bugs:
  Please report bugs to our mailing list. (See `Contacting us', below.)
  Include in the report:
    The version of Bluefish you are using
    The version of GTK you are using
    If it is a Seg fault (crash), include a backtrace 
      (see http://bfwiki.tellefsen.net/index.php?pagename=DebuggingBluefish)

Contacting us:
  http://bluefish.openoffice.nl/
  development mailinglist: bluefish-dev@lists.ems.ru
    send "subscribe" to bluefish-dev-request@lists.ems.ru to join