Created attachment 279954 [details]
sample web page to show rendering issues
Always reproducible by using the attached HTML files with 2.12.3 version of WebKitGtk using MiniBrowser running on Fedora 21 Desktop
MiniBrowser <filename> --bg-color="rgba(0,0,0,0)"
Works correctly without transparent background.
If more details are required about the different packages installed on the system, please let me know.
*** This bug has been marked as a duplicate of bug 159455 ***