We can’t say enough about these two tools when trying to diagnose an unusually slow site. Once the obvious issues have been examined (large images, bad scripts, slow database responses, damaged tables…) you should always run Firebug and YSlow sessions within your browser for further diagnoses.

Firebug first off, is a Firefox plugin that provides a wealth of information about any website or page you are currently examining. This tool will provide information about HTML, CSS, Scripts, DOM, Network, Images, Flash etc.

While loading a page, Firebug will give you some valuable network activity item by item and will reveal errors within the compiled code or the various scripts you’ve installed.

YSlow is not another application, but an additional tool for Firebug you can install for even more information and valuable suggestions. YSlow is a Yahoo development tool that will letter grade your site’s HTTP requests, DNS lookups, Javascript, CSS and so much more.