1. A method for spell checking and correcting of character strings input to a mobile device through use of keys of the mobile device, said method comprising the operations of: (a) receiving a character input; (b) determining whether the character input is a predetermined delimiter character; (c) adding the character input to a character string when said determining (b) determines that the character input is not the predetermined delimiter character; (d) performing an initial dictionary look-up for the character string when said determining (b) determines that the character input is the delimiter character; (e) performing character substitutions on at least one character in the character string to produce a modified character string when said performing (b) of the initial dictionary look-up does not locate the character string, the character substitutions being limited to other characters mapped to a common key of the keys of the mobile device; and (f) performing a subsequent dictionary look-up for the modified character string following said performing (e) of the character substitutions.