When you visit a website part of the info your browser sends to the webserver is the user-agent header. You can view the user-agent header using this webpage. Assuming you are using the default browser it should look like this:
Mozilla/5.0 (Macintosh; ARM Mac OS X) AppleWebKit/538.15 (KHTML, like
Gecko) Safari/538.15 Version/6.0 Raspbian/8.0 (1:22.214.171.124-0rpi27rpi1g)
As you can see it claims to be the Mozilla browser running on Mac, and confusingly also Safari.
You can spoof this header, but that is usually not needed. Download pages usually include a small link to other versions. However, as millways points out you won't find much software available for the Pi outside the regular repositories.
You can read more about the user-agent header on the Wikipedia page.