- image sprites are a terrible hack that adds a lot of complexity and maintenance effort to pages (though effective for loading/processing times)
- the best feature of HTML tables is still the automatic (optimal) sizing of columns when the content can vary, so fixed column widths are not possible where tables are most useful
Some advice they forgot:
- use a good caching reverse proxy (Varnish)
- don't litter your pages with ads and tracking pixels, they incur a huge slowdown usually
- don't use cookies if possible, at least not on the domains/paths all your static content is loaded from
- don't use loaded web fonts (except maybe icon fonts instead of inline images)
- don't use huge JS libraries if you don't need but a few features
- don't rely on JS libraries to lay out your page, having JS post-process your page after loading just so it looks as intended is a huge (visible) slowdown