Should I be optimizing CSS for a specific browser and screen resolution?

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 开发者_运维技巧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

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Build your site to assume a certain minimum size. say, 800x600 or 1024x768 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 (1680x1050 / 1280x1024 should handle most desktop users these days) and then adjust later as needed.

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Run google analytics on the site. Find out the real usage for your site. Maybe everyone has 24" monitors @ 1920x1080

# 2 is very skewed since internal traffic (employees) all have 1280x1024 and are very heavy site users.

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I've been following the 320 and up project. From a best practice point-of-view, it might we worth looking at:-

‘320 and Up’ prevents mobile devices from downloading desktop assets by using a tiny screen’s stylesheet as its starting point.

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I just usually design sites at a width of around 800 - 880px, no wider than that, Think my site is 880px.