Yes, but that depends on the initiation of a 'session.'

If your browser fires up inside the LAN and requests a website on port 80, you initiated a session from within the LAN, the router will allow traffic on port 80 between that destination and your computer.

If a WAN side request to initiate a session is on port 80, and as Anthony said some ISP's block port 80, then the communication will fail.

So if port 80 is 'blocked,' a computer on the internet cannot start a session with a device within your LAN using port 80, but a computer inside your LAN can start a session with another device on the internet on port 80 and it will work.