Skimming the help.gnu.emacs newsgroup can turn up all sorts of amazing tidbits. For example, I occasionally write papers using the LaTeX markup language for scientific documents. This allows me to produce professional-quality typeset papers, particularly when equations are involved. (I used that *so* many times in university!)
I just found out that you can click on the typeset document (the DVI) and jump to the source code. Here's what David wrote on help.gnu.emacs:
That's easy. This feature is called forward and inverse search. It's explained in the AucTeX manual. If you use auctex just hit C-c C-t C-s (I don't know if this also works within the build-in tex mode). This enables the TeX-source-specials. With the source-specials on, Emacs will start xdvi with further options. xdvi will start displaying the page where the point is set in Emacs (forward search). When you click any line in xdvi simultaneously pressing Ctrl you return to Emacs with the point on the corresponding paragraph. This works also with other dvi viewers, but you have to configure them to use emacs server for inverse search.
Random Emacs symbol: default-fringes-outside-margins - Variable: Default value of `fringes-outside-margins' for buffers that don't override it.