To convert an html page into aspx page,
1. Create a new web form in visual web developer.
2. Copy the content from body of the html file , paste it in body of the aspx page.
3. Similarly copy the script, meta tags from head section of html , paste it in head section of aspx page.
4.if any external style sheet,Images included with html file, add them appropriately in a folder of your asp.net application.
5.Now try to run the page and check if everything appears well, if not appearing well check the stylesheet and make some small changes.
6.Check at the top of the page asp.net , <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> it is necessary.
Practice will give you perfection in css , styling and HTML.
-------------------All should be well--------------
If you don't find any controls in code behind , add [runat="server"] attribute in markup.
and is an html control and is server control.