Sometimes when I am reading a long webpage in Firefox, I want to bookmark a specific position within the page (not just the page itself).
Is there any way to accomplish this?
The Bookmark Anywhere userscript allows you to point the mouse anywhere on the page and to set a bookmark at that place. Recall the bookmark and the place will be remembered properly, including the scroll positions.
I haven't tried it, but there's an extension called Pagemark that looks promising:
You can use Bookmarklet from http://bquot.com that does exactly what are you asking.