I attached html file with gif animation. Please open it in \qt\Demos\4.7\browser-build-desktop\release\browser.exe, then open it in Chromium browser. You will see difference. I think that gif is highly optimized so it is too complicated for Qt.
Please follow the QtWebKit bug reporting guidelines when reporting bugs. See http://trac.webkit.org/wiki/QtWebKitBugs Specifically: - The 'QtWebKit' component should only be used for bugs/features in the public QtWebKit API layer, not to signify that the bug is specific to the Qt port of WebKit http://trac.webkit.org/wiki/QtWebKitBugs#Component - Add the keyword 'Qt' to signal that it's a Qt-related bug http://trac.webkit.org/wiki/QtWebKitBugs#Keywords
It seems the animated gif attachment is missing...
Without the source GIF triggering the bug there is nothing we can do.