No! I was looking for a reason you might get a 403. If it’s not in the .htaccess file it may well be in the server’s config file. Is it actually a problem for you? It is a security measure so that people don’t see all your images if they try to access the images file.
What happens is that if there is no index document (index.html, index.php etc) in a directory, if someone goes to domain.com/images or domain.com/js etc the server lists all files in that folder. This could be a security risk (with js files particularly) or unwanted (for your images), so the server is often configured so as not to allow access to domain.com/images and domain.com/js etc. It still allows access to the files in that folder, just to the document index. And, yes, this is any directory that has no index file.
I hope this makes sense. I’m not very good at explaining this.
Pretty much. A lot depends on how things are configured and set-up.
AFAIK in general it’s something like
HTTP Request for a folder.
eg. http://mysite/somefolder/
If there is an index.php file serve that
If there is no index.php file, but there is an index.html file serve that
If there is neither an index.php nor an index.html file show a list of the folders content.
IMHO Options -Indexes is a lot easier than putting “nothing to see here” files in folders, but it is commonly done.