First of all, CSS is used to control the design of a page. It does not control any content, at all.
Now, moving onto your question. You can certainly use ASP to do what you want, but it's not quite as easy as you would think.
As far as I know, you can't use ASP code within your include statements, so you would have to search for some ASP code to retrieve the information from the reports, then print it out on the screen.
Whereas, with PHP, you would simply do something like:
PHP Code:
include('report_'.$_GET['report'].'.txt');
You have to be a little more creative with ASP. As I said, you'll have to find some code that can read the information from a file into a variable. Then, you can use the Response.Write command to print that information out on the screen.
I'm not sure what format the crystal reports come in, so I don't know which code to point you toward, unfortunately.