I have this <div class='divname'>...</div> where I use this in many other pages.
Instead of repeating this code can we create a html file and include it in aspx page? if yes how?
I am not using Masterpage, and my backend is vb.net
Instead of creating separate html file, you can create User Control. If you are trying to create separate html you need to specify all the tags for e.g.
<html><head></head><body></body></html> etc.
In User Control you can just add your code like <div class='divname'>...</div>