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Website Performance.

Website Performance. How websites works? DNS LookUp. Rule 1:Make Fewer HTTP Requests. 10 -20% response time involves in retrieving the HTML page. Remaining 80 -90% Response time spent in making HTTP requests for all components.(Images, scripts, stylesheets, Flash etc.). Some Techniques :.

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Website Performance.

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  1. Website Performance. • How websites works? • DNS LookUp.

  2. Rule 1:Make Fewer HTTP Requests • 10 -20% response time involves in retrieving the HTML page. • Remaining 80 -90% Response time spent in making HTTP requests for all components.(Images, scripts, stylesheets, Flash etc.)

  3. Some Techniques : • Image Maps • CSS Sprites • Combined scripts and stylesheets

  4. Rule 2 :Add an Expires Header • Use Far future expires header on components that changes infrequently. • Use expires header on Images, Scripts , Stylesheets.

  5. Rule 3: Gzip Components • How compression works ? • Request Header: • Accept – Encoding: gzip,deflate • Response Header: • Content – Encoding: gzip • What to Compress? • Scripts • Stylesheets • Static pages

  6. Stats :

  7. Rule 4: Put Stylesheets at the Top. • Progressive Rendering. • To reduce white blank screen effect.

  8. Rule 5: Put scripts at the bottom. • Parallel downloads: Browsers download two components in parallel per hostname.

  9. Parallel download using two hostname.

  10. Parallel downloading is disabled while script is downloading. • Scripts blocks downloads

  11. Worst case: Scripts at the Top

  12. Best case : Scripts at the bottom.

  13. Rule 6: Make JS and CSS External • Use inline scripts only in Home page • In all secondary pages, Use External files. • If every page on site uses same JS and CSS files, using external files will results in high reuse rate for these components. • Use Post-Onload download.

  14. Rule 7: Reduce DNS Lookups • Browser takes 20 -120 milliseconds to lookup the IP address of given hostname. • Avoiding DNS lookups cuts response time, but reducing parallel downloads may increase response times. • Guideline says to split components across at least two but no more than four hostnames.

  15. Rule 8: Minification/Obfuscation of JS • Minification: Remove unncessary characters , whitespaces,comments. • Obfuscation: It is like minification, but it also convert long function and variable names in smaller strings. • Minification should be used. • Tool for Minification : JSMin

  16. Some stats 85K: JS size without JSMin & gzip compression • 68K: JS size with only JSMin (21% savings) • 23K: JS size with only gzip compression (73% savings) • 19K: JS size with JSMin and gzip compression (78% savings)

  17. Some other Rules: • Avoid Redirects • Avoid Duplicate scripts. (Make sure scripts include only once.)

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