Windows 8 includes one HTML5 browsing engine that powers two browsing experiences: the new Metro style browser and IE10 on the desktop. The common HTML5 engine provides strong support for Web standards and a consistently fast, safe, and powerful Web programming model for both browser experiences as well as for Metro style applications. You can read more about the new Metro style browsing experience on the Building Windows 8 blog.

With this update, IE10 includes support for touch-friendly sites to use many new technologies:
Rich Visual Effects: CSS Text Shadow, CSS 3D Transforms, CSS3 Transitions and Animations, CSS3 Gradient, SVG Filter Effects
Sophisticated Page Layouts: CSS3 for publication quality page layouts and application UI (CSS3 grid, flexbox, multi-column, figures, regions, and hyphenation), HTML5 Forms, input controls, and validation
Enhanced Web Programming Model: Better offline applications through local storage with IndexedDB and the HTML5 Application Cache; Web Sockets, HTML5 History, Async scripts, HTML5 File APIs, HTML5 Drag-drop, HTML5 Sandboxing, Web workers, ES5 Strict mode support.