good answers, I'm reading/learning about fragment identifiers now.
I can say that "#.UIWXAHYknB4" is coming from add-this script I recently put in a fixed div at bottom of page. Before I've always served images (bookmark) from my server or simply written Bookmark (text) instead of image.
So that's the why 'now' answer.
I'm reading here:
jenitennison (dot) com/blog/node/154
Oh, using <!DOCTYPE html>. CSS called with SSI as doctype.txt - just FYI