Here's a quick tip to boost your source code browsing speed:
If you need to constantly go back and forth between a few spots in code, place (toggle) a bookmark by pressing CTRL+B+T , then you can always go to the next bookmark by pressing
CTRL+B+N or to the previous bookmark by pressing CTRL+B+P
UPDATE: As simontew points out in the comments, the exact key mapping depends on your mappings. See this article for more details.