QuickLook HTML plugin?

Solution 1:

You are looking for qlcolorcode. qlcolorcode allows you to have syntax highlighting in your quicklook preview:

Solution 2:

qlcolorcode didn't display HTML files by default on my installation of 10.8. I could get it to display them by adding public.html and public.xhtml to CFBundleDocumentTypes:LSItemContentTypes in ~/Library/QuickLook/QLColorCode.qlgenerator/Contents/Info.plist and logging out and back in.

You could also remove /System/Library/QuickLook/Web.qlgenerator/, but it also handles webarchive and svg files. Removing the entries for public.html and public.xhtml from the Info.plist didn't seem to work.