ATG

Prospectus Summary

THIS SUMMARY MAY NOT CONTAIN ALL OF THE INFORMATION THAT IS IMPORTANT TO YOU. YOU SHOULD READ THE ENTIRE PROSPECTUS, INCLUDING THE FINANCIAL STATEMENTS AND RELATED NOTES, BEFORE MAKING AN INVESTMENT DECISION. AS USED IN THIS PROSPECTUS, THE TERMS "WE," "US," "OUR" AND SIMILAR TERMS REFER TO ART TECHNOLOGY GROUP, INC. AND NOT TO ITS MANAGEMENT OR STOCKHOLDERS.