More typos on web.md

[turbomarc]

Typos on web.md

Line 8: Missing "the"
HTTP is the protocol for sending requests to ---[the]--- server and for the server to send responses to those requests.

Line 108: Should be "URLs" not "URLS"
The web browser gets to the right server with an address called a URL. Take a look at the following URL---[s]---:

Line 113: Extra "s"
If one web application---[s]--- handles all of that, it needs to track who takes care of what.

[bridgethillyer]

Thanks @turbomarc! I will make these changes.