URL Structure for Category Pages

[ron15]

I'm developing a site that will have multiple categories within the broader niche. Here is how I'm planning on doing my URL's:

mysite.com
mysite.com/category1
mysite.com/category2

All pages within a category would have .html file like:

mysite.com/category1/page.html

I'm interested in feedback to my category page setup. It will be a mixture of text, maybe some small images, and links to all the pages within the category. As it is, I don't have a .html extension on the category pages, its just as above. My thought is that I'm trying to present a logical grouping of pages to the search engine and users.

Is my approach okay? I'm wondering as this will be my first medium to large site and I'd like to get off to a good start. I've already started the content with .html and I'd like to keep it that way. Does it matter that my category page has no extension? Would I be better off with mysite.com/category1.html and then mysite.com/category1/page.html?

[ergophobe]

I like to think that the URL structure should reflect the navigation in some way (not necessarily an exact 1::1 correspondence, but have the same overall structure). So ideally if the user lops off a term from the navigation, it should lead to a logical navigation.

I usually prefer URLs without file extensions, but if you're going to use one, .html is the closest you can get to none at all (sort of like www is as close as you can get to using the root domain without actually using it).