Mobile Web Design Help

Can anyone help me find a good resource for information on mobile web design? More specifically, I'm interested in "responsive" web design where a single website (and related code) can be used both by a desktop and mobile browser.

Is there a way to code your HTML/CSS to recognize the device your user is using and display the appropriate webpage?

There just seems to be so many features/changes to the design of some pages when viewed on a mobile browser and my knowledge of CSS/HTML doesn't encompass this.

Any help is appreciated. Thanks!