I had a site built for me, and in the main directory there is an index.html and an index.php. Is there a point of having both the php and the html index? Normally I'm just use to an HTML file.
Well, I wouldn't go on deleting anything. You should ask your developer for certain. Your site might run off the index.php file or the index.html file. You can download them both to see what they contain. I would be weary about just going ahead and deleting!
Well, I think you should point to your Browse and type: yourdomain.com/index.html and yourdomain.com/index.php to see what really is the different between those. Usually, in many cases, people use .php to intergrate their site to their forum (such as displaying members online, ...) But I prefer to use .html since it's SE friendly URL However, if having .php and .html doesn't give you any problem, then I don't think you should delete it.
No difference between index.html and .php for SEO what so ever. Ask the developers and also check it out yourself in the browser and the files themselfs. Chances are if they added the index.php its because they are going to use php for your websites.
Yep, I have index html and index php on the same domain. This allows me to have a forum in the same folder without having to go to www.domain.com/forum . The default will normally be .html so by having two index pages people will not see the forum until they click on the link. You can have your flat html site running in the same folder without problem. All the links on the forum will be pointing to index.php anyhow. This might not be the case though, and there might be some other reason.