There are several ways to do Smalltalk code syntax highlighting on a web page. Pier has Pier-Shout, found on Lukas Renggli's Monticello repository. For browser-side highlighting, there are Alex Gorbatchev's Syntax Highlighter and Software Maniacs' highlight.js.

This site is using highlight.js. It is loaded in my Smalltalk rendering code thusly:

html script source: '/highlight.pack.js'; 
    type: 'application/javascript'; 
    with: [].
html script type: 'application/javascript';
    text: 'hljs.initHighlightingOnLoad()'.