The icons assigned due to what the System thinks created them based on their file extension ( and sometimes by their resource fork, I think, when they actually have one ). OS X assumes that you will be using Safari, so it may assign Safari icons to any 'html' file it sees, until and unless you use Safari to assign a different browser as the default. Actually, any local ".html" file will open BBEdit when I double-click it because that's what I use to edit them. When surfing, of course, they come in to the browser, so they work fine that way. As I understand it, icons are purely for decoration and human consumption, although they can be marginally useful for telling what program the System thinks should open them.
Unless these files are extremely large, I'd suggest leaving them alone. Or, at most, move them to your desktop and see if things operate normally for a few days. There are probably over 150,000 files on your disk, a few dozen extra will not make much difference. It's generally a bad idea to mess/delete items unless you know for a fact that they are corrupt or unneeded.
For bookmarks, I still rely on URLM Pro so they are all available in any/all browsers and any other app, for that matter. I've never looked for nor bothered any 'bookmark' files in any browser, since I don't need/have any, other than what may have come with the app.
