What is SeaMonkey Composer?
SeaMonkey Composer is an HTML (Hypertext Markup Language) editor that allows you to create and edit web pages. Composer is a WYSIWYG (What You See Is What You Get) editor, so you can display how your page will look to the reader as you're creating it. It is not necessary for you to know HTML, since most of the basic HTML functions are available as commands from the toolbars and menus.
SeaMonkey Composer allows you to edit documents in two views: design view and HTML view. The HTML view lets you edit the HTML source code if you so desire. To view or edit the HTML source code, open the View menu, and choose HTML Source, or click the "<HTML> Source" tab in the "Edit Mode" toolbar at the bottom of the Composer window.