Holmes is a CSS stylesheet for diagnosing potentially invalid, inaccessible or erroneous HTML markup.
holmes.css is useful for checking the quality of your code (up to W3C HTML5 standards), nitpicking over ensuring markup is valid and semantic and accessility guidelines are met, and when you are tasked to fix up and debug an old, OLD website. It has a simple implementation and a mostly unobtrusive effect on your page. Not recommended for live enviroments.
Remember too that these are just guidelines: if something is flagged but you can’t change it for a good reason, don’t worry about it 🙂 Also use a validator if you want to be 100% sure.
It works by adding a class to the <body> tag and highlights elements with:
When a highlighted item is hovered, an informative message explaining the “reason” is displayed.
And, there is also a bookmarklet provided which can activate Holmes for any website instantly.
Compatibility: All Modern Browsers