so the past couple times i have gone onto my yahoo email, and it says "Safari cannot verify the identity of the website altfarm.mediaplex.com blah blah blah." i have no idea what this is. i googled it and found some people who had asked about it on some message boards but i couldnt understand the responses (I'm not good with the technicalities of computer problems).

Anyways, if anybody knows what this is please let me know. Thanks a lot.
Oh and I'm on Leopard OSX 10.5.1, if that helps.

Ad server.

In layman terms, thats where all the ads in your browser come from.

so should i be worried about anything? or just ignore it?

Just ignore it. It just means that your connection to the advertising server isn't being done through a secure connection. Like that would matter in any case.

Even if you wanted to buy something off the ads, it's the connection to the seller that would need to be secured anyways. It's pointless to care if someone can see the ads that are being sent to you -- assuming someone's actively sniffing your connection.