Web design
< style > .left, .right { float : left ; width : 20% ; /* The width is 20%, by default */ } .main { float : left ; width : 60% ; /* The width is 60%, by default */ } /* Use a media query to add a breakpoint at 800px: */ @media screen and (max-width: 800px) { .left, .main, .right { width : 100% ; /* The width is 100%, when the viewport is 800px or smaller */ } } < /style >