I am new to the world coding as well as CSS and would like to know if I should optimize CSS to a specific browser.
Also should I be concerned about screen resolution? If so what screen sizes should I be targetting especially if I have very little information about the end-users e.g. will they using laptops with smaller screen resolutions in comparison to desktop, will they be using netbooks, etc
Build your site to assume a certain minimum size. say, 800×600 or 1024×768 and enforce that with min-width/min-height directives. If you want to support mobile browsers, have an alternate layout that assumes a much smaller screen
But as far as assuming sizes, there’s very little you can do without running a sniffing bug in Javascript that reports back to your site (or use something like Google Analytics). Until you’ve got some statistics, pick a decent middle-ground (1680×1050 / 1280×1024 should handle most desktop users these days) and then adjust later as needed.