Best Practices for Speeding Up Your Web Site

Yahoo's Exceptional Performance team has published a number of best practices for making web pages fast on the Yahoo Developer Network.

See http://developer.yahoo.com/performance/rules.html for the full list but some of the highlights are:

Minimise HTTP requests by using CSS sprites, image maps and inline images.

Put Stylesheets on top (to the document HEAD).

Put Scripts at the bottom as they block parallel downloads, so may delay the loading of other resources like images.

Reduce the number of DOM elements to improve the performance of DOM access in JavaScript.

Split components across domains to maximise parallel downloads. You can create a couple of extra sub-domains for this purpose.

Minimuse the number of iframes.

No 404s: only show informative 404 pages where appropriate — not for images and JavaScript files.

Choose <link> over @import.

Keep components under 25K as the iPhone won't cache components bigger than 25K (uncompressed size).

Avoid empty Image src as some browsers will waste server resources handling these.

There's plenty more tips there so it is well worth a read.