Recommended Validation Tools
Here are some recommended tools to validate/test your site for the web awards. We are not saying that you have to use them. We are just saying that they are good tools.
SiteValidator provides sitewide HTML/CSS validation. If an error is found on one page or more it groups errors and warnings with a number of times it occurs. It also provides a report on each page validated in the site. It can do deep linking as well. SiteValidator now has integration with an accessibility checker - Tenon.io - through API calls. SiteValidator requires an account and registration can be for a month or for a year. Entrants get a 25% lifetime discount if they purchase an account before 20 August 2016. Go to the pricing page and sign up for the most appropriate account for you or your agency.
W3C Unicorn Validator provides as many conformance checks as possible.
W3C HTML Nu Validator is a no DOCTYPE validator.
W3C HTML Validator. Use the option Group Error Message by type to see unique errors for your web page.
W3C CSS Validator will help you check for CSS errors.
It is very important to keep in mind that to date, no website evaluation tool has been developed that can completely replace a human being. This is because with present technology it is difficult to emulate human attributes such as common sense. In this regard, the results that they produce should be interpreted in context with the website you are evaluating.
Tenon.io requires an account for deep linking and use of the API. There is a free service, however it shows only the basics.
AInspector Sidebar is an extension for Firefox.
Functional Accessibility Evaluator 2.0 requires an account to get reports.
Paciello Group's Contrast analyser is available for both Mac and Windows.