What is Fern?

Fern is a very configurable HTML syntax checker. Using Fern, you can check HTML syntax for missing tags, malformed tags, browser compatability issues, accessability issues, and much more.

Unlike most HTML syntax checkers, Fern is designed for maximum usability and configurability.

• Usability.

  Off-line

  Many HTML syntax checkers only work on-line. For example, Bobby allows you to enter a URL for it to check, then it returns the results in an HTML page.

  In contrast, Fern runs from the command-line, allowing you to run it "off-line" and on your local web pages.

  Command-line

  Fern is designed as a command-line application. But it can easily be "associated" with other files. For example, under OS/2 or Win95, you can associate the Fern executable with all HTML files, allowing Fern to run when you "double-click" on the HTML icon.

  With other applications

  Fern's biggest limitation is that it cannot "download" web pages for syntax checking; Fern only runs on local files. But, Fern can be used with web-downloading programs such as Templeton. Templeton downloads each HTML document and can run Fern on each retrieved file. Fern has also been used in conjunction with GNU's "wget"¹. This allows for rapid syntax checking of files directly from the web.

  With other applications

  Fern, as part of the Templeton suite of applications, can either be used as a stand-alone application or with other programs.

• Configurability.

  Soft-coded

  Many HTML syntax checkers have hard-coded how they run. The tags that they check, the error messages displayed, and the version of HTML that they know are all "programmed in". This can quickly cause problems when the checker "does not check what you want" or "says too much (or the wrong thing)". With the rapidly changing look of HTML, users generally need to wait for the software designer to release a new version that supports the "newest" HTML version.

  Rather than hard-coding messages, Fern uses a "definition" file that describes what to look for and what type of response to display. The definition file is in plain text, allowing anyone to edit the file.

  If you don't like a particular message, change or remove it.
  If you want Fern to look for a new HTML syntax, add it.

  In contrast to "hard-coded" applications, Fern is "soft-coded", allowing the user to change how the program works.

  "On-the-fly" changes

  Fern allows conditions to be specified before each run. These conditions can be set from the command-line when you start Fern. For example, the standard definition file generates text-based syntax reports. But if you want to have the output in HTML, just add "HTML_OUT=TRUE" to the command-line.

  Similarly, Fern's standard definition file does not check for browser-specific HTML code. Netscape, for example, offers a large number of "extensions" to HTML. (These "extensions" are non-standard and only work under Netscape browsers.) If you want Fern to check HTML code designed for "Netscape browsers", you would add "Netscape=TRUE" to the command-line.