TCP/IP Protocol Architecture Model: This is about the layers of programming that allows the Internet to operate worldwide

 TCP/IP Protocol Architecture Model

OSI Ref. Layer No.	OSI Layer Equivalent	TCP/IP Protocol Examples
5,6,7	Application, Session, Presentation	NFS, NIS+, DNS, telnet , ftp , rlogin , rsh , rcp , RIP, RDISC, SNMP, and others
4	Transport	TCP, UDP
3	Network	IP, ARP, ICMP
2	Data Link	PPP, IEEE 802.2

1 more row

Introducing the Internet Protocol Suite (System Administration ...

The problem is that these layers allow mainframes and servers to communicate with computer, laptops and IPad like devices and Smart phones and some cell phones that are not smartphones and any other devices I failed to describe or mention here.

So, in order to do this you need ways for all these types of hardware to communicate through different operating systems and architectures worldwide. So, when you look at this the very top layer has to be HTML and other similar languages like Java.