I've been using MS Frontpage 2003 to maintain our company website for years. Looking for a replacement that can:Import/convert a MS FrontPage website and modernize it (clean up the HTML to make it standards compliant, etc.)Supports (or converts) the substitutions (Include Page and Text substitutions that are done when the page is published (so they become static HTML).Leverages my knowledge of FrontPageLooks like the likely contender is Web Expressions but I'm open to objective suggestions. 
What is a good replacement for MS Frontpage?
software
Expression Web will do what you need to do. It should be comfortable for you to use since you're familiar with the Microsoft UI paradigm. It also corrects a number of problems that the old Frontpage had.While there are some other very good web editors available there will be a significant learning curve for them.