make yourself a dll that either inherits a specific control, or inherits UserControl if it is a composite control.

upload the dll to your website

then in your html page

Code:
<object id="abutton"  classid="http://yoursiteaddress/button.dll#namespace.classame">
    <param name="Text" value="Test">
</object>
and that is it, minus security settings that may need to be set on the client including setting the website as a trusted site..