LJ's tag system doesn't handle that condition as it should.
Clicking on the . tag sends you to:
It really ought to send you to:
I guess that's not a legal URL however.
A little more experimenting yields a few more glitches:
Clicking on a tag that's .. will cause you to climb up to http://m-leprae.livejournal.com
Clicking on tag that's ../friends sends you to my friends page.
Example entry at: http://m-leprae.livejournal.com/294364.html
There may be worse things one can do, but I'd rather not go there.