This is a list of tools and techniques to optimize your website.

Benchmarking Tools: 

1) Pingdom: 

http://pingdom.com/

Pingdom offers everything from simple to very advanced server, network and website monitoring services. Pingdom offers you the ability to monitor your servers and infrastructure 24/7, all year long. We have a multitude of monitoring servers placed all over the world with just one goal in mind: To alert you as soon as any of your servers, networks or services fail. Pingdom gives you full control over your infrastructure. 

2) Websiteoptimization: 

http://www.websiteoptimization.com/

Using free website speed test will help you find out if slow pages are hurting your business. It will test page size, composition, download speed and point out some of the things that need to be done to increase your on-line competitiveness.

3) ab - Apache HTTP server benchmarking tool:

ab is a tool for benchmarking your Apache Hypertext Transfer Protocol (HTTP) server. It is designed to give you an impression of how your current Apache installation performs. This especially shows you how many requests per second your Apache installation is capable of serving. 

Quality Assurance Tools :

W3C Quality Assurance Tool :

http://www.w3.org/QA/Tools/

 This page lists some of the tools provided by the W3C in the domain of Quality Assurance: validators and other test tools. Almost all of these tools are web-based, are available both as downloadable source, and as free services on the w3.org site.