Google rejiggered its search algorithm 450 times last year, in an effort to improve the quality of results.

Google is typically tight-lipped about it the inner workings of its search business, but there are a few nuggets worth looking at in a Popular Mechanics interview with Udi Manber, the Google vice president who oversees search quality.

The job of the algorithm is to best match Web pages with people's search terms. One tweak the company tried last week was increasing the "diversity" of search results so the listed Web pages would cover a broader scope in an attempt to compensate for the ambiguities of search terms, he said.

While some might see the industry of search engine optimisation (SEO), which strives to get Web sites higher placement on search sites, as gaming the system, Manber said that at least a basic amount would make his life easier.

"I wish people would put more effort into thinking about how other people will find them and putting the right keywords onto their pages," he said.

He also said Google doesn't adjust search results by hand.

"If we find, for a particular query, that result No. 4 should be result No. 1, we do not have the capability to manually change it," he said. "We have to find what weakness in the algorithm caused that result and find a general solution to that, evaluate whether a general solution really works and if it's better, and then launch a general solution."