There are plenty of ways to determine if our site is running slowly—arguably one of the most well known is YSlow by Yahoo available at https://developer.yahoo.com/yslow/. In the following screenshot, it is shown in use from within Firebug:
YSlow is perfect to establish where there are slow elements in our pages. It uses a number of rules based on research by Yahoo's Exceptional Performance Team to work out how well a site measures up against its standards for performance.
Let's take a look at using it to see if some well-known sites could be improved. As an example, we'll begin with installing YSlow as a plugin for Firefox.
Note
This example assumes we are using Firefox with Firebug already installed; if it is not already present, then you can download and install it from http://www.getfirebug.com.
There are various ways to install YSlow. They include using a bookmarklet, browser add-ins, or working directly from the command line. The most convenient is a browser...