/* Where contains the characters: A to Z, a to z, 0 to 9, underscore (_), and comma (,) as a separator.

Note:

Upper case A = 0, B = 1 and so on to Z = 25.
Lower case a = 26, b= 27 and so on to z = 51.
Zero (0) = 52 and so on to 9 = 61.

Reference: http://code.google.com/apis/chart/#top */