Changed these. See my [extended commit message](https://github.com/oerpub/github-book/commit/a0dc62667d3f7a043ff11983202f5376c7db9804) for details. The `cursor: url()` stuff was me copying some Aloha code and trying to be compatible with more browsers. All `url()`s are problematic? There are some for `background-image` and `content` in the code ... some by me and some by others.