I happend to check heroku for one of our friend to see how difficult is to upload files in Heroku.
After login into account I got the understanding , it is not simple to add static files in heroku and no support HTML files as default, as they use GIT to upload files and make the version of your software/code.
As per official update you have to look at the this link for the understanding:
Static html in Ruby
But it is not easy and simple for everyone and it is technology specific as well.
So I searched little and got the idea, here you have to trick heroku to update static files.
I assume you are using windows 7.x,8.x
1) Very first thing install heroku ToolBelt
2) Create folder/directory in your system like C:\heroku or d:\heroku etc....
3) open command prompt (CMD) from start->run
4) go to your newly created directory