Thanks for your reply.
The problem is if the search result is more than one page, then the 2nd page link shows
http://shop.com/search.php?mode=search&page=2
I have the problem when first search "monkey" , the page 1 is correct, the page 2 is correct.
Then I search for "rabbit", the page 1 is correct, the page 2 shows monkey's items because the page 2 link is the same
http://shop.com/search.php?mode=search&page=2
xcart gives the old searched page