There are a variety of tools available that can help testing and optimizing website performance:
LoadStorm – Developers can utilize this tool to check load time of the website. This tool allows its users to create as many test plans, scenarios, and steps as it requires. Tests can be built using the tool in such a way as to simulate a large number of different users with unique logins and different tasks.
SiteAnalysis – This tool can be used to test and validate critical components of a website. It helps in testing and validating internal and external links, domain names, DNS servers, and SSL certificates. This can be run as and when required as often as every hour, or as infrequent as once a week.
Avalanche – One more load testing tool specifically created to test security, network, and Web application infrastructures by generating large quantities of user and network traffic. It works well with multiple Web browsers, and supports Web Services testing Supports HTTP 1.0 / 1.1, SSL, FTP, RTSP / RTP, MS Win Media and more.
VisualVM- This Free tool helps in testing Java applications. It automatically detects and lists locally and remotely running Java applications while monitoring application performance and memory consumption.
HTML Validator- This add -on from Mozilla adds HTML validation inside Firefox and Mozilla. It can indicate the number of errors of a HTML page visible as cons in the status bar. A user can easily see Error details on the HTML source of the page for correction.
Fortify 360- This is security as well as vulnerability detection tool for the website. It features integrate static source code analysis, dynamic runtime analysis, and real-time monitoring to identify and accurately prioritize the greatest number of critical security vulnerabilities.
XenoCode Browser Sandbox – This is an important test tool for developers before launching a website is Browser testing. This tool offers a series of virtual applications that can run all popular browsers simultaneously. It does not even require the installation of software.
W3C HTML Validation Service- This validator checks the markup validity of Web documents in HTML, XHTML, SMIL, MathML, etc. If you wish to validate specific content such as RSS / Atom feeds or CSS stylesheets, MobileOK content, or to find broken links, there are other validators and tools available.
Google's Website Optimizer- The testing service from Google which enables its users to test the desired content and pages. Generally used for testing headlines, images, or text using web-based system. The testing helps analyzing impacts on conversions, user actions, traffic, or other goals.
DeviceAnywhere – This mobile handset testing tool helps in developing, deploying, and testing of content on more than 2000 real handsets devices in live global networks around the world via the Internet.
I hope these tools will help freelance web developers in bringing out a user-friendly and error free website. Please share your suggestions and feedback on the same.