Hdfc maestro debit card?

i have an kids advantage account in hdfc bank...i am 15 years old and have got a kids advantage debitcard which is maestro and it is said tht it can be used internationally...so i tried using it online in some sites like ebay and others...but it does not accept the card....can maestro be used to buy online...if can please tell me where i can try using it online...the soul purpose of my getting this debit card was buying online..so plz i would appretiate answers....