<head>
<link rel="stylesheet" href="//fiendish.github.io/gh-fork-banner/gh.css">
</head>
Then
<span id="gh"><a href="https://github.com/<username>/<projectname>">Fork me on GitHub...lol</a></span>
- Pure CSS
- Glows on mouseover
- Window-width-based positioning
- "lol"
See the demo: https://fiendish.github.io/gh-fork-banner/index.html