I found this on another site, dealing with the same issue:
Well here is some follow up but I don't have a definitive solution as I don't have this issue to test and I use a different akamai server to login to Facebook (I have no control over that - but it's something to look into). This issue is fairly well prevalent on the net and this thread is currently number two with Google keyword "a248.e.akamai.net".
The issue that most of you guys are running into is at login.facebook.com which kicks you over to get the security certificate, s-static.ak.facebook, on akamai servers. If you get this error with other websites, then that particular certificate is also being hosted by akamai servers. The reason why some people or zone alarm thinks that a248.e.akamai.net is suspicious is because akamai is a content host provider and has hosted nefarious items in the past, maybe even currently. However, blocking a248.e.akamai.net is not going to help you login to Facebook.
What I would try to do is verify that a248.e.akamai.net is currently a valid certificate. I'm not sure about other browsers but in Firefox you can go to Tools -> Options -> Advanced ->View Certificates -> Servers -> Add Exception. Add a248.e.akamai.net and you will most likely get a message about the certificate being a trusted valid certificate and that there is no need to add an exception. If you don't get that message, then add it.
The other thing you could try is removing any certificates associated with a248.e.akamai.net in the same window and maybe removing any certificate associated with login.facebook.com. First select the certificate and export, just in case you need to import it back later. I would also look for a248.e.akamai.net in Tools -> Options -> Advanced -> View Certificates -> Authorities and remove them there also (remember to export first). The reason behind this is to get rid of any expired certificates. Keep in mind that this a shot in the dark so if anything breaks...well....sorry.
As a final shot-in-the-dark, ping a248.e.akamai.net, and add the IP address as an exception. The issue with this is that you are associating a valid certificate to an IP address and the IP address might associate to a site in the future that doesn't have your best interests in mind. You should still be okay through a combination of the expiration date and the fact the certificate hash needs to associate with the issuing certificate provider, though, I'm not 100 percent clear on this. Maybe someone else can comment on that.
As far as all browsers doing this, check the Hosts file, clear DNS through flushing on the local machine and rebooting the router. It might help to use a third party DNS provider like OpenDNS or DynDNS. Ultimately, my gut feeling is that this on Akamai's side and not your own.
