Google plans to change its back-end servers so that some users will automatically use an encrypted HTTPS (Hypertext Transfer Protocol Secure) connection when they use Gmail. Gmail users can already read their messages via HTTPS, but to do this they need to click a “browser connection” box at the bottom of the settings page. Under the test, HTTPS would be turned on by default. HTTPS can be used to securely connect part or all of a Web page. Google Docs and Calendar users can connect via HTTPS as well, but there’s no setting to make this permanent. Users must simply type in https:// every time they connect to these services.
More Info: Online Security Blog