YSlow is a tool that analyzes the speed for a web page. It is a plugin that you can install in Firebug. While running a report, the site will be tested on some parameters. A report will be shown with an overall score of your website.
The test is based on a ruleset. You have the YSlow (V2) and YSlow (V1) ruleset. We will use the YSlow(V2) ruleset for this recipe, which has 22 rules. The complete page load (including images and static content) can be increased by 25 to 50 percent if you adhere to the following 22 rules:
Minimize HTTP requests
Use a Content Delivery Network
Avoid empty
src
orhref
Add an expires header or a cache-control header
Use Gzip for components
Put stylesheets at the top
Put scripts at the bottom
Avoid CSS expressions
Make JavaScript and CSS external
Reduce DNS lookups
Minify JavaScript and CSS
Avoid redirects
Remove duplicate scripts
Configure ETags
Make AJAX cacheable
Use GET for AJAX requests
Reduce the number of DOM elements
No 404 errors
Reduce the cookie...