Providing second content items in association with first content items

A computer program product embodied in a non-transitive computer-readable medium including instructions, that when executed, cause one or more processors to:

• receive, at a server and from a requesting device, a first call for content to be published in a content item slot on a resource associated with a publisher, wherein the first call for content is generated by execution of a given tag included in the resource;
• determine that the publisher has authorized one or more additional content item calls to be automatically initiated by the server responsive to the receipt of the first call;
• determine, by the server, a first content item responsive to the first call;
• generate, by the server, a message that causes the requesting device to initiate a second call for additional content independent of other tags embedded in the resource;
• provide, by the server and to the requesting device, the first content item and the message responsive to the first call;
• receive, by the server and from the requesting device, the second call for content that was generated in response to the requesting device;
• process the second call;
• determine, by the server, a second different content item responsive to the second call;
• and
• provide, by the server and to the requesting device, the second different content item for publication on the resource along with the first content item.

A system comprising:

• one or more processors;
• and
• one or more memory elements including instructions that, when executed, cause the one or more processors to:
• receive, at a server and from a requesting device, a first call for content to be published in a content item slot on a resource associated with a publisher, wherein the first call for content is generated by execution of a given tag included in the resource;
• determine that the publisher has authorized one or more additional content item calls to be automatically initiated by the server responsive to the receipt of the first call;
• determine, by the server, a first content item responsive to the first call;
• generate, by the server, a message that causes the requesting device to initiate a second call for additional content independent of other tags embedded in the resource;
• provide, by the server and to the requesting device, the first content item and the message responsive to the first call;
• receive, by the server and from the requesting device, the second call for content that was generated in response to the requesting device;
• process the second call;
• determine, by the server, a second different content item responsive to the second call;
• and
• provide, by the server and to the requesting device, the second different content item for publication on the resource along with the first content item.