Do you have to use .html in URLs?

Happy Monday all!

When you create a landing page in Marketo, Marketo automatically appends .html to the URL. For the purposes of promoting the URL in print, can we leave the .html off to make the URL look cleaner? e.g. pages.mycompany.com/hello rather than pages.mycompany.com/hello.html

We've tested this and it seems to work, but I wanted to be sure that there aren't some pitfalls I'm unaware of.

Thanks,

James