The following features have been updated:
Features that may not work
Any site with extensive use of custom CSS/Script in 2010 may not render the same design/branding in 2013. Refer to APAN Applications Governance 2.B and 5.A.3.
Public view for lists created in SharePoint Designer or XSLT customization
These views or their list web part views may display an error after the upgrade. Site Owners may have to re-add the desired web part.
ASPX Page design / layout features appear changed
Fonts, top banner/header size & position alignment (left/right/center), text size, and colors may render differently compared to what was viewed in the 2010 version. The visual upgrade may also render the web parts in a completely different order than what appeared on 2010 pages. Site owners may need to make changes as necessary.