This is a good article about what Ebay's designers have learnt about redesigning a large website with a large audience. Read on...

One of the most interesting bits is here:

A few years ago, when eBay designers opted to change the background color of every page from yellow to white, they actually changed the shade of the pages in almost imperceptible increments daily for months, until the pages were finally white. "If they'd flipped a switch and gone from yellow to white, everyone would have screamed," said eBay senior usability engineer Laura Borns. "But no one had any complaints about it, because it was so gradual."