Client side web site performance

Smaller images,
Omitting quotes in HTML attributes (yes, people went that far!),
Using fixed width tables in IE 5
Balancing server response buffering vs creating the whole page first and then sending it all in one response, etc.

Putting images on different domains (though now other resources are worth considering too)
Compressing the server output using gzip (a bit hit and miss on earlier versions of IIS though)
Cache control using the Expires header
Use CSS (though in those days I used it mostly for font definitions and browser sniffing was needed to load different CSS files!)


Use GZip on all text-based output (which should be optimized anyway via web standards!)

Try to reduce the number of HTTP requests (e.g. combine CSS and JavaScript files during development or during the build process, use CSS sprites, if possible etc)
Help browsers ensure they can cache as many of your files as possible

Let browsers download your page resources in parallel even though HTTP 1.1 limits you to 2 concurrent requests from a domain (through sub-domains, minimizing or eliminating loading CSS and JavaScript in a way that blocks the browser, etc)

Disperse your content through things like content distribution and extra sub-domains (though be aware of extra DNS-lookups that might result)