In Netscape Composer’s Preferences, there is a section for “Composer”.
I recommend setting “use CSS styles instead of HTML elements and attributes”. This doesn’t affect the editing functionality of Netscape’s editing toolbar, but it does allow you to more reliably add much greater stylistic variation to your web pages.
“Retain original source formatting” or “Reformat HTML Source” controls whether Netscape reformats any HTML you type in. As a beginner, you may wish to have Netscape reformat your source; later, you may wish to change this to retain your own formatting.