UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G/A DEALERTRACK HOLDINGS INC Common Stock 242309102 Item 1. a. Dealertrack Holdings, Inc. b. 1111 Marcus Avenue c. Suite M04 d. Lake Success, NY 11042 Item 2. a. D.F. Dent & Company, Inc. b. 2 East Read Street, 6th Floor Baltimore, Maryland 21202 c. Incorporated in the State of Maryland d. Common stock e. 242309102 Item 3. Investment adviser registered under section 203 of the Investment Advisers Act of 1940 Item 4. a. 2,054,239 b. 4.96% c. 1. 2,054,239 2. 0 3. 2,054,239 4. Item 5. N/A Item 6. N/A Item 7. N/A Item 8. N/A Item 9. N/A