how do you do this ? (no need to reload pics etc on similar pages)

hi, I have seen a number of web pages that have this thing whereby images = that appear on every page, such as the header logos etc..., do not = reload each time a page is opened (for example see=20 http://www.muze.nl/software/examples/addressbook/index.phtml?firstletter=3D= E when changing the letter in this addressbook the image at the top does = not reload.) From what I can gather this is not via frames. Does anyone know how to = do this ???? (hope i'm not offtopic - i don't actually know whrether = this can be done in php...) nick