See http://googleblog.blogspot.com/2009/09/now-s-u-p-e-r-sized.h...

A little (maybe) inside story here

Believe it or not, I guess Google globally adjusted it's box height after Google China added 6px to its search box height.

On 13th April this year there's a post on a extremely popular & influential IT commentary news site in China

http://www.cnbeta.com/articles/81765.htm

saying that Google.cn failed to match Baidu.com because their search box is so small that people need exta time to move the mouse to focus the correct text box

6 days later Google.cn improved one of their page(specifically http://www.google.cn/hp?sp=china) accordingly

http://www.cnbeta.com/articles/82222.htm

Next on 6th October Google.cn switched to bigger search box on all of their pages, including the google.cn home page

http://google.org.cn/posts/google-china-bigger-search-box.ht...

Finally on 10th September Google globally adopted this design change

http://cnbeta.com/articles/93034.htm

Coincidences?