Comment 19 for bug 455943

for me at least commenting out line 51 of /usr/share/gwibber/ui/templates/defaultcss.mako fixed it

  background-image: url('');
  background-repeat: no-repeat;
/* -webkit-border-radius: 3px;
*/ -webkit-box-reflect:below 0px -webkit-gradient(linear, left top, left bottom, from(transparent)$
}