Providing a content item from an online system to a third party system that modifies the content item for presentation in accordance with a layout specified by the third party system

A method comprising:

• receiving, at a third party system, a request from a client device for a web page;
• retrieving a markup language document for the web page, the markup language document including instructions that, when executed by the client device, cause the client device to:
• render a frame within the web page, the frame including a content item obtained from an online system, the content item having components including a title, image or video data, and a landing page specifying a network address of additional content for the client device to retrieve in response to an interaction with the content item;
• generate the web page based on layout information included in the markup language document;
• and
• position one or more components of the content item obtained from the online system at locations within the web page based on the layout information included in the markup language document;
• and
• providing the markup language document to the client device, which is configured to execute the instructions included in the markup language document to display the web page.