It very much depends on the type of website you want to make. When you are learning, the best way is to look at other sites that look and feel similar to what you are trying to achieve, and look at their CSS. Do not copy their CSS directly, but try to understand how they implement different parts of the design.
In general, since you are following the route of a fluid layout (the best way for a general IMO site), it is to provide relative values for width, etc., and follow this with absolute values for min / max values for width, etc. For example, for your container div in your design, there might be something like the following:
div.contentbox
{
width:80%;
min-width:800px;
max-width:1280px;
}
You may need to look at the floating divs to make sure they stay aligned at different sizes of the browser, you can see how to focus on the centers using margin:auto.
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