Jeannete,

Are you familiar with flash player from Macromedia originally and now owned by Adobe?   PDF files that are often viewed using Acrobat?  The list goes on and on.  these and many others are add ons to Firefox, IE, and others.

 To find out what plugins are installed, type "about:plugins" without the quotes in the URL (address) bar and hit return.  A list of installed plugins will show up. 

 
twinlabs has a good comment about add blocking software.  Much of what could cause it depends on how M* wrote the page and with what tools.  But addition of software that blocks some of the commands to the browser would be another likely cause.

jb