Online tool for webmaster: usability, performance, SEO

SEO

This is an instant, free and no-registration tool to analyze the SEO performance of a URI for a given key phrase. Reports include a variety of useful information and structured recommendations to improve overall effectiveness. Try a few reports and judge for yourself. The tool aims to encourage the use of standards compliant, user-friendly and accessible code while at the same time helping website-owners to attract more visitors to their websites. Of course, no automated tool can substitute for a human analysis by an experienced search engine optimizer.

Validation

This validator checks the markup validity of Web documents in HTML, XHTML, SMIL, MathML, etc.

A lot of other validation tools are available: RSS/Atom feeds or CSS stylesheets, MobileOK content, or to find broken links

Usability

Website Optimizer, Google’s free website testing and optimization tool, allows you to increase the value of your existing websites and traffic without spending a cent. Using Website Optimizer to test and optimize site content and design, you can quickly and easily increase revenue and ROI whether you’re new to marketing or an expert.

userfly.com provides instantaneous web user studies by recording user visits and letting you play them back to see every mouse movement, click, and form interaction. Conducting a user study doesn’t have to be expensive or a logistic nightmare. With userfly.com you can perform simple and cheap user testing with your real users. Not free, but as low as 10$ to start a usability campaign.

Accessibility

WAVE is a free web accessibility evaluation tool provided by WebAIM. It is used to aid humans in the web accessibility evaluation process. Rather than providing a complex technical report.

This is how a report look like, WAVE shows the original web page with embedded icons and indicators that reveal the accessibility of that page.

Performance

A free web site speed test to improve website performance. Enter a URL to calculate page size, composition, and download time. The script calculates the size of individual elements and sums up each type of web page component. Based on these page characteristics the script then offers advice on how to improve page load time. The script incorporates the latest best practices from Website Optimization Secrets, web page size guidelines and trends, and web site optimization techniques into its recommendations.