before start, you must get your feet wet into html and css.
have some patient, read all through the topic about html at here:
http://www.w3schools.com/html/default.asp[
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then read all the topic about css at here:
http://www.w3schools.com/css/default.asp[
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after that you can start in ASP.NET.
A good book that you can start with (A well explained step by step guide):
Download:
Visual Studio 2008 - Beginning ASP.NET 3.5 in C# 2008 From Novice to Professional
For more info, look for ebooks about asp.net in the internet, google, yahoo, bing.
use keywords "ASP.NET beginner" to search ebooks, pdf at
http://isohunt.com[
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there should give you a good start.