6. A non-transitory computer-readable storage device having computer executable instructions stored thereon, the computer-executable instructions configured to cause a processor to perform acts of: receiving an advertisement with Ad keywords associated with the advertisement; performing a semantic analysis to the plurality of phrases; segmenting content of the advertisement into a plurality of phrases; selecting top-ranked phrases from the plurality of phrases based on the semantic analysis to form a reduced subset of phrases; generating a query list having a plurality of queries by combining each phrase in the reduced subset of phrases that has less than a defined number of words with another independent phrase in the reduced subset of phrases to create queries comprising two or more words; for each query within the query list, performing an internet web search to identify a set of descriptions, each description describing a search result from the internet web search; analyzing the set of descriptions to select a second set of phrases denoted as a query expansion feature set for each query; ranking the second set of phrases within each query expansion feature set and a frequency over all query expansion feature sets; generating an expanded Ad index by selecting from the ranked second set of phrases a subset of phrases as an ad expanded feature set that is combined with the Ad keywords associated with the advertisement; and when receiving a second content for display at a client device, selecting an advertisement from a plurality of advertisements based on the expanded Ad index.
6. A non-transitory computer-readable storage device having computer executable instructions stored thereon, the computer-executable instructions configured to cause a processor to perform acts of: receiving an advertisement with Ad keywords associated with the advertisement; performing a semantic analysis to the plurality of phrases; segmenting content of the advertisement into a plurality of phrases; selecting top-ranked phrases from the plurality of phrases based on the semantic analysis to form a reduced subset of phrases; generating a query list having a plurality of queries by combining each phrase in the reduced subset of phrases that has less than a defined number of words with another independent phrase in the reduced subset of phrases to create queries comprising two or more words; for each query within the query list, performing an internet web search to identify a set of descriptions, each description describing a search result from the internet web search; analyzing the set of descriptions to select a second set of phrases denoted as a query expansion feature set for each query; ranking the second set of phrases within each query expansion feature set and a frequency over all query expansion feature sets; generating an expanded Ad index by selecting from the ranked second set of phrases a subset of phrases as an ad expanded feature set that is combined with the Ad keywords associated with the advertisement; and when receiving a second content for display at a client device, selecting an advertisement from a plurality of advertisements based on the expanded Ad index. 11. The non-transitory computer-readable storage medium of claim 6 , wherein the second content for display further comprises at least one of a web page or a search result.