From MozillaZine Knowledge Base

Two things about the page you get when you edit an article:

The link called "Cancel" next to the "Save page" and "Show preview" buttons currently points to the wrong place. It points to "Editing help", whereas it should point to the original article.

Secondly, please please could you make the edit page contain a preview of the existing article (ie. exactly like what you get when you run "Show preview" with nothing new typed into the source box). This is because you often want to see how the existing stuff is formatted before adding new stuff. I imagine most people have a couple of "Show preview, make changes, show preview, make changes" runs, and each "Show preview" page allows you to see the existing formatting and edit the source simultaneously, so it seems unnecessary to prevent the editor from seeing the existing formatting when he first opts to edit the page.