I recently came across an interesting project which required to open an HTML file inside the CD-ROM using the default browser on the users side. There are two ways, both are equal in terms of complexity and flexibility.

Method 01:
This uses the standard ShellExecute command.

[autorun]
shellexecute=index.html
label=Autorun HTML
action=Open index.html

Method 02:
This method requires you to download a small executable and put it within the contents.

[autorun]
open=autorun.exe index.html
label=Autorun HTML
action=Open index.html

Please note that the above examples only shows a few of the options you can use in a Autorun.inf file. For other possible entries, please refer to MSDN.