cant access certain websites,has something to do with ports listed above
on my PC
Ports are used to represent services that a user is using. Port 80 is for general web browsing (http://....). Port 443 is the secure version of port 80 (https://... notice the "s", for secure). And the last one, port 21, is used for incoming file transfers, i.e. downloading.
If you're experiencing this with multiple sites, sounds like you might have a web security software running on your computer/network. Are you at work, or on a public network? It could be that your company has a proxy server in place, or the establishment you're at has blocked certain sites they deem inappropriate.