A method for providing an advertisement is disclosed. The method, to be implemented on a machine having at least one processor, storage, and a communication platform connected to a network may include receiving a request for an advertisement to be inserted into a content page to be presented to a user. The method further includes selecting an advertisement relevant to the content page and the user based on a content-advertisement index and a user-advertisement index, constructed based on user browsing context, and transmitting information indicative of the selected advertisement as a response to the request. Further disclosed is a method for generating multi-dimensional index. The method, to be implemented on a machine having at least one processor, storage, and a communication platform connected to a network may include generating a content-advertisement index based on at least one content profile and at least one advertisement profile, and generating a user-advertisement index based on at least one user profile and the at least one advertisement profile. The content-advertisement index and the user- advertisement index are used to select a relevant advertisement to be inserted in a content page that is presented to a user.