1280 x 1024 at home, 1600 x 1200 at work, but: The actual window space usable for your site will vary according to the type of browser, what toolbars the user has added and so on. Hardly anyone will have their browser window maximised; you'll never get the full screen resolution to play with. The gallery on my site is mostly 800 x 600 images, although I sometimes give a link to a larger version.