It walks and talks like a credit card but is not made of plastic. It's made of virtually nothing! Citibank launched its new virtual credit card that runs on the MasterCard network this week. Citibank's new 'ClickCredit' is a separate line of credit to be used exclusively for online purchases. Citibank is offering two versions of the program 'Click Citi Platinum Select' and 'Click Citi AAdvantage'.  While these lines of credit are not issued in the form of a credit card, they carry many credit card features such as cash back rewards, airline mileage rewards and purchase/protection guarantees. 'Click Citi Platinum Select' members will receive 2% cash back on all Internet purchases made through May 31, 2000; thereafter they will earn 1% cash back. 'Click Citi AAdvantage' members will earn two American Airlines 'AAdvantage' miles for every dollar spent online, through May 31, 2000; thereafter they will earn one mile for every dollar spent. 'ClickCredit' customers also receive 'Price Protection' and 'Extended Warranty' protections. 'Click Citi Platinum Select' customers also receive 'Purchase Assurance'. The 'Platinum Select' version offers a 0% APR for three months followed by a Prime +1.65% APR. 'ClickCredit' customers can monitor their spending and make payments at www.citibank.com through features such as 'Account Online' and 'CitiPay'. Citibank's 'Account Online' service enables its traditional credit card and 'ClickCredit' customers to log on and manage their credit accounts. 'CitiPay' allows customers to make payments over the phone or online by deducting them directly from any checking or savings account. Consumers can apply online for a 'Click Citi Platinum Select' or 'Click Citi AAdvantage' account.  Online applications can be accessed directly at www.clickcredit.com, or through the Citibank Cards web site at www.citibankcards.com.  Customers will be issued 'ClickCredit' cards which will include their account number; the cards are for reference only and are not used when actually making a purchase.