16. The non-transitory computer readable medium of claim 15 , wherein the operations further comprise: identifying, from the one or more character strings included in the content feed, a second matching character string that matches the particular resource locator; and determining that a first priority of the matching character string is greater than a second priority of the second matching character string, and wherein the content item is selected from a set of content items that corresponds to the matching character string based on the determination that the first priority of the matching character string is greater than the second priority of the second matching character string.
17. The non-transitory computer readable medium of claim 16 , wherein each matching character string is a matching regular expression that specifies a set of matching character strings.