just build a fluid layout, and make all your font-sizes in relative widths (% or em, I use YUI's Fonts CSS to make this easier), and the font sizes will scale when the user increases/decreases the font size in their browser.

Your question is very vague btw theres a million things you could mean by it and some are really dumb so elaborate. When you say you want it to work on standard/widescreen, from 800x600 up to 1800x1600 (or whatever, any sizes of resolution is what you mean), what exactly do you mean? The only want to ensure that your site works on a small resolution, is to make the maximum width of your site that resolution. if you want your site to display well on an 800x600 resolution, then make your site 800px or less wide. You can create a fluid layout, in which, say, you have a left column that is 20% of the screen width and a right column that is 80%, and then no matter what their browser size is, the site will stretch. This is a bad idea for a lot of sites because if it's too wide, your site will look like shit.

Also the current minimum acceptable resolution is 1024x768, and the general consensus on site width's is generally in the 960px area (or just make it easy on yourself and use YUI's Grids CSS, which supprts 3 common widths for sites).

Also what do you mean in the first sentence where you know how to make an image that's bigger than the screen resolution be shrunk to fit? You should never ever have to change the size of an image in HTML code to make it "fit" in anything. It should be the size you need it otherwise you are wasting bandwidth, download time, and storage space.

I'm not exactly sure what you are asking for though! Are you just asking for general guidelines to making your site accessible or what?