Accuracy of search results over web is improving steadily due to ongoing incorporation of semantic web technologies into traditional information retrieval approaches of the present web. These semantic technologies along with knowledge base they contain are being exploited at large scale by all mainstream web search engines to provide conceptually precise search results to satisfy user's efficient information needs on web. In this paper, first, semantic search and its key concerns have been explored and discussed. Second, it revisits various semantic search approaches which process and consume knowledge from semantic technologies to improve precision of search results. Thirdly, keyword to concept mapping is revisited and illustrated using domain Ontology. Finally, key design issues of search engines incorporating semantics have been revisited.