Let's take a look at Neilson with the numbers, which tell the story of how we optimised a large scale web site. There were four key aspects we were trying to improve: download times for the overall framework, optimising and compressing files to reduce latency, and most importantly, the physical file sizes.
Files reduced to 58 from 135
Download size compressed to 498.9 from 936.8
Page load time down to 2.75 from 4.85
General HTML for pages has been reduced; this has helped with the W3C validation which is now completely compliant.
Files reduced to 5 from 7
Download size compressed to 68.5 from 125.7
Page load time down to 1.96 from 4.81
Reduce embedded code from social media networks, for example the Twitter buttons pull in the whole API Javascipt.
Files reduced to 6 from 11
Download size compressed to 111.6 from 134.0
Page load time down to 0.43 from 1.47
Optimise, optimise, optimise. We looked at every aspect of the stylesheet and optimised new and existing styles. The stylesheet was then minified and set to compress when served by the web server.
Files reduced to 1 from 4
Download size compressed to 14.1 from 14.4
Page load time down to 0.14 from 0.21
With images the philosophy is to remove, compress and consolidate. Unnecessary images, such as buttons, have been removed from pages where not used. Many of the images have been reassessed for compression and uncompressed images have been fixed. Finally, consolidating images for icons and buttons into a single sprite image greatly improves download times and latency.
Files reduced to 45 from 110
Download size compressed to 303.9 from 531.8
Page load time down to 1.97 from 2.53