Totem?
 

When I go to play a web movie I get this error message;

Totem could not play 'file:///home/fvs/.mozilla/firefox/tleow4nu.default/Cache/FD373215d01
You do not have a decoder installed to handle this file. You might need to install the necessary plugins.

How do I correct this problem?

What type of web movie, give a link to one you're talking about...

Looks like you might be short some codecs though.

IGF

First u have to say what kind of the file u r going to play...
okok
Have u installed w32 codecs..?
if not better to install that first....;Then u may get the file correctly....:)