perhaps it makes the job easier but when it comes to making a functional website, anything from notepad onwards is good to go.
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edit2: i'm losing the plot i think, i dono

i've not had any legal drugs today (tobacco), below are just other method's.. the Particletree link i'd say it the best to stick with, for learning and as such later ability.
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here's something that may well do you..
http://dynamicdrive.com/dynamicindex9/info3.htm
to covert for dynamic css, in theory replace the lines window.location:
Code:
window.location.replace("http://www.netscape.com");
with a document.write, printing out the name of the css file for the detected res:
Code:
document.write('<link rel="stylesheet" type="text/css" href="smallstyle.css">');
although, there could be newer methods.. alternate stylesheet?? i'm not upto speed but someone may know if/how it can be used.
edit:
alternate stylesheet example:
http://dynamicdrive.com/dynamicindex9/stylesheetswitcher.htm
to blend with the above replace window.location with
Code:
chooseStyle("800600", 60);
800600 being a title attribute of the alt style tag.
the javascript for this function should be on a line above the res detect script. the function must exist before being called.