Whenever my girlfriend tries sending me a link via IM on Yahoo, if it comes as a hyperlink (i.e., she put the http:// ahead of it), then Yahoo takes it upon itself to take the domain name, and convert it to the IP address of the respective website. Clicking on this fails to produce a website. It’s been doing this over several months and years, and I’m finally at the point of frustration where I want to fix it.
What appears in the address bar when you click on the link? If I ping www.google.com and then use firefox to go to the address directly it works no problem. I don’t think all websites will respond to ip address directly but google.com seems to.