Blocked incoming traffic, why possible to get traffic?

[!!!@!!!]

Hi!
I can't understand,
when ISPs block all your external IP's ports and the incoming traffic
on them, then how it is possible to open a web page and request
information from it, and then the web page server can send the
information (incoming traffic) to your external IP and you get the
information without being blocked.
For example:
I login to facebook and facebook server sends to my computer's
browser
the html code of the home page.
How can this information pass the block of the ISP???

[Char Jackson]

On Mon, 13 Sep 2010 09:24:21 -0700 (PDT), "!!!@!!!"
<eltoni.91@gmail.com> wrote:

>Hi!
>I can't understand,
>when ISPs block all your external IP's ports and the incoming traffic
>on them, then how it is possible to open a web page and request
>information from it, and then the web page server can send the
>information (incoming traffic) to your external IP and you get the
>information without being blocked.
>For example:
>I login to facebook and facebook server sends to my computer's
>browser
>the html code of the home page.
>How can this information pass the block of the ISP???

Please crosspost rather than multipost.

[!!!@!!!]

On Sep 13, 8:38*pm, Char Jackson <n...@none.invalid> wrote:
> On Mon, 13 Sep 2010 09:24:21 -0700 (PDT), "!!!@!!!"
>
> <eltoni...@gmail.com> wrote:
> >Hi!
> >I can't understand,
> >when ISPs block all your external IP's ports and the incoming traffic
> >on them, then how it is possible to open a web page and request
> >information from it, and then the web page server can send the
> >information (incoming traffic) to your external IP and you get the
> >information without being blocked.
> >For example:
> >I login to facebook and facebook server sends to my computer's
> >browser
> >the html code of the home page.
> >How can this information pass the block of the ISP???
>
> Please crosspost rather than multipost.

Sorry!
Didn't know how to crosspost but now I learned. :)