Example use:
- \[[googlecalendar html="""
+ \[[!googlecalendar html="""
<iframe src="http://www.google.com/calendar/embed?src=adkrdken8mupngh13jshlbenoc%40group.calendar.google.com&title=OSEL%20Calendar&chrome=NAVIGATION&bgcolor=%2371d873&height=588" style=" border-width:0 " width="480" frameborder="0" height="588"></iframe>
"""]]