24. A non-transitory computer-readable medium storing software comprising instructions executable by one or more computers which, upon such execution, cause the one or more computers to perform operations comprising: receiving, by a client device, a web resource from a server; determining, by the client device, that the web resource includes a particular trigger term, from among a predefined set of trigger terms that are associated with answer box search queries, wherein an answer box search query is a search query for which a search engine responds with an answer to a search query instead of with links to web resources; generating, by the client device, a modified version of the web resource, wherein the modified version of the web resource includes an answer box gadget in association with the particular trigger term; providing, by the client device, the modified version of the web resources, including the answer box gadget, for display to a user of the client device; determining, by the client device, that the user has selected the answer box gadget; in response to determining that the user has selected the answer box gadget, transmitting, by the client device, an answer box search query to the search engine, wherein the answer box search query indicates the particular trigger term; receiving, by the client device, an answer to the answer box search query from the search engine; and providing, by the client device, a representation of the answer to the answer box search query for display.
29. The medium of claim 24 , wherein determining that the web resource includes the particular trigger term further comprises determining that the web resource includes a category trigger term associated with a particular category of answer box search queries.