--> Catalog and Contacts modules are removed.
This modules were source for shop and Listers and Php listers pages, so all this page types are not supported in V4 anymore and are replaced by new page types : Mysql Shop and Mysql catalog.
--> Ligtbox Slideshow is replaced by Multibox Slideshow, but exeisting slideshows are automatically converted
--> Overlib Hints are replaced by Mootools Tooltips, existing hints are partially converted to new system, but because of changes to tooltip styles (tooltip styles are now project styles), colors of old overlib hints are not kept
--> Templates : V4 only supports updated templates (read templates with editable template option enabled)
--> Fonts : V3 XXXL style is removed (this change was necessary to make editable headings)
--> Calendar Page: V3 calendar pages created without preset, will be without formatting in V4, to fix this, go to calendar settings tab --> Calendar Layout and select one of the presets.