A tremendous increase in the use of the Internet for online communication is witnessed worldwide. Yahoo! Inc., provides one such service in the form of Yahoo! Groups. Each such group is identified and accessed using a unique group identifier. This paper presents digit-wise statistics and a detailed analysis of the usage of digits based on the study of nearly 1,400 unique Yahoo group identifiers containing digits. The results show that one-fourth of the total usage of digits is contributed by the digit 0, whereas the three digits 0, 1 and 2 collectively contribute more than 50% of the total digit usage. A number of areas that influence the selection of a digit or digits by the users in the design process have also been identified. To the best of our knowledge this is the first attempt to study online user behavior based on the usage of digits for designing a unique online identifier.

The growth of the Internet has provided the users of 21^st century with a new means of communication. According to Jones and Fox (2009), instant messaging, social networking and blogging have gained ground as communication tools, but e-mail remains to be the most popular online activity. Besides these, other online activities include sharing views and discussing various topics through groups and discussion forums. Yahoo! Inc., is one company that provides such Internet services worldwide. The specific services provided by Yahoo! Inc. include mail, news, search, groups, video and maps, to name a few. Yahoo! Inc. was founded in 1995 and Yahoo! Groups, which provides one of its services, came into existence in 2000 (Wikipedia, 2010a).

The Internet Marketing Definitions website (www.internetmarketingdefinitions.com) describes Yahoo! Groups as a service that operates as both electronic mailing list and Internet forum. Members can post and read messages either by receiving them in their e-mail account or by going to the group's homepage. Since the inception of Yahoo! Groups, there has been a tremendous increase in its user bank. This service allows the user to create a group address and provide a group name. Technically speaking, the group address is one that is used to uniquely identify a Yahoo group. In order to mean its intended usage, we use the term Yahoo-group identifier or simply identifier for unique Yahoo-group address. In the current work, we have concentrated only on group addresses and not on group names which can consist of any character combination and are meant to provide a brief introductory description line of the group.

There are a few research instances which throw light on statistical analysis of character usage. Even of those available, most of the works have concentrated on the usage of characters as a stylometric parameter. Aaronson (2000) has listed a set of 15 features which are important for performing data-driven stylometric analysis. These features are: ampersand sign, apostrophe, colon, comma, dash, dollar sign, exclamation mark, forward slash, left parenthesis, percent sign, period, question mark, right double quote, right parenthesis and semi-colon.

Information Technology Journal, Textual Analysis of Digits, Yahoo Groups, Yahoo-Group Address, Yahoo-Group Identifier, Internet Marketing, Statistical Analysis, Stylometric Parameter, Instant Messaging, Social Networking, Electronic Mailing List, Unsolicited Bulk E-mails.