- Minimise number of source files css and js included in the html. The initial load time is sensitive to the number of files to be processed.
- Avoid source file loads of css and js on client side. These end up as serial operations (in contrast to the usual parallel browser operations). This is a significant factor even if these url are cached.
- Avoid un-cached images (icons and the like). With references buried in css and js files, these seem to take a long time to load and also fall into the serial operations category.
If you are using Twitter Bootstrap or similar toolsets, this is hard to achieve. Repackaging the css to enable fast loading undoes most of the benefits of using Bootstrap :(