I keep getting this odd message

[saltire]

When i go into active convos or into a thread, i get a meassage in a banner across the top of the screen, covering the Rosabella Gregory ad. it says
"This website wants to run adobe somthing or other. Click here if you want to install it"
Or words tot hat effect, but only in active convos or a thread, not on home page, or topic list!

Adobe Flash Player it says, and also if you trust the website and the add on, click here!

Is no one else getting the message?
Why is it there, and is it a mumsnet thing or just my PC?

it probably means the advert has some content that requires flash player and you don't have it installed on your pc.

It is not a problem to install it (both not difficult and no risk to your pc) - many websites use it - so if you want to see what you are "missing" install it - otherwise ignore the message.