Quick doubt about HTML5

hi, im trying to be a webdeveloper. Learning the basis with Deitel's book and came a quick security server question...

In a Deitel's example ( Chapter 3 fig 3.1 ) http://pastebin.com/YxWtCUe7

line 44: <input type = "email" placeholder = "name@domain.com" required /> (name@domain.com)

In google chrome I can easily change the attr REQUIRED and erase. Then, I can submit the POST to server.

Tell me guys, in a "real world application web client-server" this can be a problem? Cuz if I can really send this query to server so I'll need to make input check in client AND server side.

regards,