TiddlyWiki is a single self-contained, self-modifying HTML file that does not require any server whatsoever. Installing it is as simple as downloading initial template file to your disk. Being text file, it is searchable, mergeable, etc. Copy it on a USB stick, put it in a dropbox folder and you got your backups. But don't get fooled by the apparent simplicity, it is a full blown wiki, with themes and plugins, if you want them.
Or Firefox. Firefox will also send you to the open tab if you try to go to an URL you already went to, instead of opening a second instance of the same page.
Last write wins. Although tiddlywiki does detect the situation when file was changed on disk, there is not much you can do at this point. Before tiddlywiki I used to use pmwiki on a server and it has the ability to merge changes (via diff3). I miss that dearly in tiddlywiki.
Ok, it is a text file, a web page, but why so complex an interface? I feel it is very weird to have the content of paragraphs inserted just below the TOC in http://www.tiddlywiki.com/ (I am guessing this page showcases TiddlyWiki, right?)
Simple anchor links should work much better, and would not break the back button.
