The "SingleFile" plugin is a better version of ctrl+s. It will save all pages as single html file and even include images as an octet stream in the file so they aren't missed.

I would be careful in mirroring a site. It's very likely to violate copyright or similar laws, depending on where you are. I think archive.org is considered fair use, but if you put it on a personal or even business page it might be different. For example Google News in EU is very limited in what content they may steal from other web pages.