Optimizing client-side performance involves reducing HTTP requests, properly distributing page resources, minimizing file sizes through techniques like gzip compression and minification, leveraging browser and proxy caching through proper cache control headers, and using content delivery networks to distribute content across multiple servers closer to users. Key techniques include reducing the number of components and images on pages, making scripts and stylesheets external, using image sprites, optimizing DNS lookups, enabling compression, setting long cache expiration times for static assets, consistently versioning files to invalidate caches, and placing popular files on a CDN for faster delivery.

1. Optimizing Client-Side Performanceby Andrew Ivachewsky

2. MotivationEnhance User Experience

3. Accept Slow Networks

4. Meet Performance Requirements

5. Improve Website ConsistencyHTTP Requests ReductionReduce number of page components

6. Make stylesheets and scripts external

7. Create sprites for CSS background images

8. Create image maps for page images

9. Always use same path to the same resources: http://www.testdomain.com/image.gif is not equal to testdomain.com/image.gifDistribute Page Resources ProperlyKeep stylesheets at the top

10. Keep scripts at the bottom

11. Remove duplicate scripts

12. Strive to make page render progressively

13. Browsers download no more than 2 resources in parallel per hostnameThink About User Experience

14. DNS LookupDNS takes about 20-120ms to resolve IP

15. DNS information is stored at OS DNS cache and browser cache