Internet Explorer 11 introduces an updated Flexbox implementation, support for CSS border images, horizontal text in vertical writing modes, zoom-independent fixed positioning, and a number of improvements in East Asian and bi-directional text layout.
In IE11 you can define custom border images with the border-image property from the CSS Backgrounds and Borders Module Level 3 W3C specification. Using the border-image property, you can specify your own images for borders as an alternative to traditional border styles.
To learn more, see Border images.
East Asian and bi-directional text improvements
In IE11, we've improved East Asian and bi-directional text scenarios, fixing a number of bugs in the areas of Ruby, line-breaking and bracket pairing (such as with parentheses and curly braces).
In September 2012, the CSS Flexible Box ("Flexbox") Layout module was published as a W3C Candidate Recommendation, incorporating some changes in certain aspects of the specification. IE11 updates flexbox support with these changes, which include renamed properties, renamed property values, and more. Moving forward, you should use the new, unprefixed names (and values) and update existing sites accordingly.
For more info, see Flexible box ("Flexbox") layout updates.
Horizontal-vertical text support
In IE11, you can render horizontal text in vertical writing modes using the -ms-text-combine-horizontal property from the W3C CSS Writing Modes Module Level 3 specification. This property is implemented behind the -ms- prefix and allows you to combine multiple characters into the space of a single glyph for the purpose of layout and decoration.