Internet browser & firewall

Whenever I install a program that opens a TCP/IP port, the firewall interrupts and asks for permission.

I have noticed that this is not the case with Internet Browsers. Why is it that firewall has not interrupted for various browsers that I have installed?

I am using Windows Fi开发者_运维知识库rewall.

Thanks.

Most browser traffic will be over port 80 and 443 which will either be open already. It could also be the case that the firewall is stateful so any connection is enabled outbound and the firewall remembers this connection and allows the return data only blocking incoming connections on that port.

Because port 80 is almost universally enabled in just about every firewall by default :)