This excerpt taken from the WBMD 8-K filed Nov 21, 2006.
Cash and Cash Equivalents, Restricted Cash and Investments
The Company considers all highly liquid investments with maturities of three months or less when purchased to be cash equivalents. The Companys policy is to maintain its uninvested cash at minimum levels. Restricted cash as of June 30, 2006 and December 31, 2005 includes money held for letters of credit securing rental leases.