I have been looking around a fair bit recently in a bid to improve performance on a number of sites… And naturally came upon YSlow for FireBug. This is a plugin that does website component profiling based on analysing the performance of all elements loaded into DOM. It examines headers, compression, size, response time, content types and can produce an accurate depiction of your worst performing scripts, stylesheets or images.

It also has a great advisory feature that uses YUI’s best practices in website optimisation (such as, gzipping components, using CDNs, marginalising background images, minimizing requests, to name but a few). It measures and ranks your site and makes you want to tweak it and improve…

I had a long play with various ways of improving but eventually came get to the best results (as speed and size gains) via some mod_rewrite .htaccess trickey:

## enable gzip page compression!
php_flag zlib.output_compression On
php_value zlib.output_compression_level 5

# compress all text & html:
AddOutputFilterByType DEFLATE text/html text/plain text/xml

<Files *.js>
SetOutputFilter DEFLATE
</Files>

<Files *.css>
SetOutputFilter DEFLATE
</Files>

# set clientside cache per element type
# 1 YEAR
<FilesMatch "\.(ico|pdf|flv)$">
Header set Cache-Control "max-age=29030400, public"
</FilesMatch>
# 1 WEEK
<FilesMatch "\.(jpg|jpeg|png|gif|swf)$">
Header set Cache-Control "max-age=604800, public"
</FilesMatch>
# 2 DAYS
<FilesMatch "\.(xml|txt|css|js)$">
Header set Cache-Control "max-age=172800, proxy-revalidate"
</FilesMatch>

This is a combination between cache controls and compression that you can tweak and deploy as needed. If you have relatively static .html or .php files, you can also try adding |html|php or whatever other extension you may see fit. Have fun.