Marco16841, if you are referring to the "Most Visited" view in the history sidebar, then an employee has said that the developers do not intend to include all the original sorting options in the new history sidebar, so it is possible that "Most Visited" will be one of these removed views.
However, you can create your own "Most Visited" smart bookmark, which should give you a similar dynamic list of the most visited websites, except that this will be located under bookmarks rather than history.
(This approach might not be preferable to having the list in the history sidebar as it originally was, but it is a possible workaround for those who want the dynamic list back.)
To give this a try:
Right-click inside any bookmarks folder (for example the Bookmarks Toolbar) and select "Add Bookmark".
Give the new bookmark a name (such as "Most Visited"), and in the URL field enter:
place:queryType=0&sort=8&maxResults=10
After saving the new bookmark, you might need to restart Firefox for it to take effect, but once it does, you will now have a folder named "Most Visited" in the selected location, which shows an up-to-date list of the 10 most visited websites.
Note, if you want to see a different number of results than 10, adjust the "maxResults" value accordingly.
