Adam de Boor, a Gmail engineer, said that many upcoming features of Gmail service will be rendered in HTML5, "Google's goal is to make Gmail load in less than a second.
"If the browser supports CSS3, Gmail will render the pages using these specifications, rather than its traditional approach of using the Document Object Model (DOM). The company has found that using CSS3 can speed the rendering time by 12%.[...]Gmail will also make use of HTML5's database standards. Now, the e-mail service uses Google Gears to store mail for offline reading, but over time that'll migrate to the HTML5 standards."
Also, a feature will allow users to drag attachments from Gmail to the desktop. To do this, his team is working on a new data transfer protocol, called "downloadurl."
Another new feature he talked about was something called "Magic iFrame," which would allow a user to take part of a Web page, rendered in a frame, and pull it out and make it its own full Web page in a new browser window.