To access web information via mobile devices is a very challenging problem since the screen size of mobile devices is limited to present the retrieval results. Therefore, many related studies propose different approaches of displaying the retrieved web documents to fit into the small screen, such as navigation by scrolling, panning and zooming. However, very few studies consider narrowing down the search space in the query formulation step. That is, query specifications can be used during the query process. This paper takes Google as an example and presents several mobile interfaces for web search by asking users to specify what kind or content of web documents are to be retrieved. These query specification interfaces are able to retrieve less but more relevant documents to users' queries. Consequently, mobile users can spend less time to browse many irrelevant documents by the general web search interface.