You're website will be built with ASP as the programming language - and the output will be HTML anyway so you don't need to worry.
I have several websites built with PHP - but the output is HTML anyway. What you need to do is make sure the HTML outputted by your site is valid and used properly for seo purposes, so you wish to have things like:
- Well structured content - use of <h1> <h2> and so on
- Content that is actually interesting and not a lot of babbling
- Meta keywords and description in the <head> of your page
- Use of proper elements such as <p> for paragraphs and <li> for list items
There's plenty of articles on this - or you could always look for someone to give you're site a review and make some recommendations.