The paid-click data released Tuesday by Efficient Frontier Inc, the world’s largest sThe company has been toying with different search box designs to see which ones lead to the most queries. As it stands, the MSN portal already accounts for half of Microsoft’s search engine traffic. Comparatively few people typed in queries straight from Microsoft’s Live.com address (now Bing.com) earch engine marketer, suggests Bing could become a significant revenue generator for the Redmond, Wash.-based software maker – if Microsoft can maintain its momentum.Though often overlooked by Microsoft watchers, the MSN portal remains critically important to Microsoft’s online business. Its home page is the crown jewel of its display ad business and MSN is also responsible for about half of the company’s Internet search traffic. And, despite the notion that portals are passe, Microsoft says its research shows that 37 percent of Internet users still rely on a portal as an important source of information.