First the whitepaper from Microsoft:
Microsoft FrontPage to Expression Web
Transitioning to Microsoft® Expression® Web from Microsoft Office FrontPage® 2003
One of the biggest differences between Expression Web and FrontPage is that Expression does not allow you to insert FrontPage "bots" -- that is, features in FrontPage that depend on FrontPage Server Extensions. In short, the "Insert > Web Component" feature in FrontPage 2002 and 2003 is not available in Expression Web, nor are Themes, Shared Borders, Include Pages, Link Bars, Page Banners, and Comments. You can read Microsoft's reasoning for this move, most of which I agree with, here: blogs.msdn.com
A key thing to realize is that Expression Web is "friendly" to web sites that use these components. It won't break them, and in fact, you can still access their properties. If you double-click on a hit counter in Expression Web, the Hit Counter dialog box will still appear and allow you to modify the properties of the hit counter. The major difference is that there isn't an easy way in Expression Web to insert a new hit counter.
In the rest of this article, I'll pinpoint some of these FrontPage components and offer alternative solutions.
Include Pages
This is the one area where I disagree with Microsoft. Include pages are a valuable way to insert content on multiple pages without having to be constrained to including that content on every page as a dynamic web template would.
The good news is that Microsoft is very aware that the community values include pages, and they will be releasing an add-on which allows Expression Web to insert and manage include pages, and will very likely include them -- or at least their functionality -- in later releases of Expression Web.
For now, you can still insert new include pages by adding a line of HTML code, namely, this:
<!--webbot bot="Include" U-Include="filenamehere.htm" TAG="BODY" -->
Simply replace "filenamehere.htm" with the URL of your include page that you wish to insert. Expression Web will recognize this webbot code and insert the include page as you would expect in FrontPage.
FrontPage Link Bars
FrontPage Link Bars have been well-used in the past for their easy-to-modify nature; unfortunately, they do not validate! Instead of using FrontPage Link Bars, use an include page that holds your CSS-formatted links, or include the links in a dynamic web template. This way, it is still relatively easy to make global changes to the navigation bar across a site by modifying the include page or DWT.
Learn more...
FrontPage Themes
FrontPage Themes have mostly been out of the template world already, with more and more developers depending on CSS for formatting the look and design of a site. Using a Theme causes your site to not validate, so you should definitely transition into CSS web sites and drop Themes altogether!
FrontPage Shared Borders
Very few template developers use Shared Borders anymore, as well. Instead, use Include Pages and Dynamic Web Templates to achieve a "global layout" for your web site. If you are not already familiar with Dynamic Web Templates, we have many resources at PIxelMill to help you become familiar with them and learn how to use them.
FrontPage Forms
You can still have FrontPage Forms within Expression Web by going to Form Properties -- the options for using FrontPage Server Extensions are still available. However, your web page will not validate if you use the options for sending to a file or an email address. Instead, find out if your web hosting provider features custom form scripts that you can use instead, or run a search query to find some free custom form scripts. You may have to learn a bit of scripting (ASP, PHP, and the like) in order to customize the scripts.
FrontPage Photo Gallery
Taking out the FrontPage photo gallery means that you will have to go back to creating a gallery page the "old-fashioned way" -- creating thumbnails, building the layout for the thumbnails, linking to your larger images. Or, look into other software that might do the work for you!
This concludes the article series on moving from FrontPage into Expression Web. I hope this series has made the transition a little smoother for you!