The important thing to do is make the distinction between clientside and serverside code. ASP is processed on the server, with all output written to the client as static HTML. Because of this the client's browser is not an issue.
It is also important to note that because all processing is done on the server first, then outputted to the client, you can't send things from the client back to the server without making a new server request, either by loading another page (or reloading the current one) - and submitting form data etc.
If you have a form, this can be written in straight html with no need to worry about asp (you only need to write it with an asp if it is any way dynamic). However, if you want to do any complex processing of the form data, such as database stuff, you'll need to submit it to an asp (or cgi program or whatever).