For a web page to function do you need to code in multiple languages? And if so, How similiar are the languages that you need to

Answer 1

I guess it depends on the applications of the website and how you want to write it.

Technically if it were only a simple webpage that listed some pictures (no zoom in features, gallery or scroll capability) and text with some links, you can easily get away with coding in HTML.

All the extra stuff adds bells and whistles: CSS to make it look prettier and be more responsive to browser size, Java, PHP and other languages for adding interface and activity outside HTML's ability, etc.

Answer 2

As Andrea said, if you want a simple page you don't need to.
Otherwise, JavaScript DOM will be helpful on handling page elements, validating forms, creating elements that access other pages without reloading it and a lot more!

PHP will handle all user informations, get user data on the database, handle the user session, validate and a loooootttt more. Go and learn! :D