border-box css
#example1 { box-sizing: border-box; }
box sizing border box
*{ box-sizing: border-box; }
boxsizing
Sintaxe formal: content-box | (en-US) border-box
Source: developer.mozilla.org
CSS box-sizing property
* { -webkit-box-sizing: border-box; -moz-box-sizing: border-box; box-sizing: border-box; }
Source: learnlayout.com