Being a designer I always felt the need of checking up a design on different browsers, especially when it involves CSS and XHTML. Clients always prefer web layouts that shows up correctly on every browser, be it the one which renders CSS correctly or the one which do not. In any case, if you have to try it, you have to download every popular browser the client wishes to have and buy mac over your PC or vice versa. But thats old crap, Evolution (of the Web 2.0 hype) has again answered the need , there are now lots of tools available for checking up a page and create a screenshots in different browser with any browser !
Tools that take screenshots on different browsers.
Browsershots.org Beta : Make screenshots from Firefox 1.0.4 / 1.5.0, Epiphany, Galeon, Konqueror, Mozilla, MSIE 6.0, MSIE 7.0 Beta, Opera 8.50, Safari 2.0. The request is qued based on the traffic and later shown the screnshot.
lixlpixel Screenshot Generator : Screenshots of layout on Safari , MacIE .