Hey Dotti
I think it's one of those things where there's no real way to tell just how much is ok for any particular child.
But, the Americal academy of peadiatrics (i think) released a study not too long ago that concluded that there was no benefit at all for children under the age of 2 in watching tv. If anything, all it did was teach them to watch tv.

The first 2 years are very important in early brain development and the stimulus that they are exposed to will shape the way their brain develops. The most important stimulus for babies is one-on-one interaction with people (and particularly mum).

Kids learn from people, not tv shows. They learn by watching, interacting and doing. They learn by using their imaginations - that's a big problem for kids raised on tv and computer games.

so, this is something I worry about too. I'm no expert, and nor am i perfect - My DS does watch tv sometimes. We've pretty much stopped watching tv ourselves when he's around, though, and save it for after he's gone to bed (i'm sure it can't rot our brains). They just get mesmerized by it, don't they?