Your index.html file is the default file that opens up when a someone visits your site. Like when someone types in yoursite.com it will auto direct to the index.html
All other supporting web html and image files, etc are ok to upload as long as the are related to your website.
Edit: You may think why not upload everything to the webserver. Eg: Your working .psd files, etc. Problem is that your provider may not allow particular file extensions.
Or your web-provider may allocate you a limited amount of file space. The files you upload use web-space. So it's wise to use it for your website.
Last edited by waynenort; 09-01-2012 at 02:09 AM..