Go Up has been one of my favorite firefox add-ons for a long time: for any site with a well-defined URI structure, it is easier to just
go up a level rather than searching for the navigation links on the web page.
the only thing i did not like was the fact that the extension did not treat fragment identifiers as navigational structures. so
going up from
http://dret.net/netdret/publications#wil02h took you to
http://dret.net/netdret/ instead of
http://dret.net/netdret/publications. for web sites using fragment identifiers, it would be more convenient to be able to
go up from a fragment to the complete resource (i.e., to simply strip the fragment identifier from a URI if there is one).
after proposing this change to the author of Go Up, he responded almost immediately (thanks, stephen!) with a new version implementing the new behavior (it will be released soon). the nice thing is that this change breaks nothing, and makes navigation on sites using fragment identifiers much more convenient.
this is one more reason to install Go Up, it is just a small button in the navigation bar and you will like it and wonder why it's not there by default. it will also make badly designed sites a bit less attractive, because you cannot navigate them using URIs.