On horizontal lists, such as for navigation menus, how are sites such as HSBC.co.uk and http://www.commbank.com.au/corporate/ getting those dividers (vertical white lines) between each item. they are clearly images but ive gone through them with firebug and can't find them.

it's something id really like to apply but it seems like a dumb question to ask. im asking it anyway as it's doing my head in!