The only code web developers copy and paste is the long, weird, pesky XHTML DOCTYPE definition.
With HTML5, you can simplify the DOCTYPE definition of your webpage. Actually with HTML5, the use of DOCTYPE is no longer mandatory.
But we should continue using older DOCTYPE definition for some time as older browsers ask for it.
Here is how HTML5 simplifies the code,
Older doctype definition:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
Doctype definition with HTML5:
All latest browsers – Firefox 5+, Chrome 12+, Opera 11.50+ fully supports HTML5 including the new DOCTYPE definition for websites.