With each new release of Windows Internet Explorer, support for the World Wide Web Consortium (W3C) Cascading Style Sheets (CSS) standard has steadily improved. Internet Explorer 6 was the first fully CSS, Level 1-compliant version of Internet Explorer.
This is an easy to understand article about the Promise pattern for Javascript. It is a way to have a 'continue with this function when this previous one succeeds' that doesn't involve nesting functions.
The jqXHR objects returned by $.ajax() as of jQuery 1.5 implement the Promise interface, giving them all the properties, methods, and behavior of a Promise.