the advantage of putting .html extension on ulrs

I have an app on A开发者_Go百科SP.NET MVC 3 and I am using routing to handle my requests as you guess. But I have seen some websites that are putting .html extensions after on their URLs. I could do the same with my app and tell the IIS to render html as an asp.net page.

I am wondering if there is any SEO or some other advantage to do that?

---

According to this article from the official Google Blog the important thing isn't how they look, but how they work. It's a long article with a lot of interesting stuff which could offer you some knowledge on how to create your URL's.

---

Historically, people thought that dynamic pages did not perform in search engines as well as static ones.

This is largely nonsense in general, so it's purely an aesthetic thing. The more elements/keywords in a URL the worse it probably is although it is negligible.