If you are web developer or architect, I would recommend reading this ebook. It explains how to make your asp.net website secured. I believe not most of users need to consider "ALL" those points, but you should perform some of important points to secure your asp.net website.
I was planning to make a list of important considerations from this book, but since this book is very well written i personally like most of points i have read so far.
And finally if you have developed asp.net website which is accessible through internet, than check whether your website do pass against security scan.
Asp.net website security analyser
Hope this book help you too :)