QR codes are a popular type of two-dimensional barcode. They are also known as hardlinks or physical world hyperlinks.

QR codes store up to 4,296 alphanumeric characters of arbitrary text. This text can be anything, for example URL, contact information, a telephone number, even a poem! QR codes can be read by an optical device with the appropriate software. Such devices range from dedicated QR code readers to mobile phones.

For more information check out Google's QR codes documentation.

The jQuery uQR is a jQuery plugin written by Marius Stanciu, a plugin that will allow you to embed QR codes into your web pages.