IPython/frontend/html/notebook/static/css/layout.css

.border-box-sizing {
    box-sizing: border-box;
    -moz-box-sizing: border-box;
    -webkit-box-sizing: border-box;
}

/* Flexible box model classes */
/* Taken from Alex Russell http://infrequently.org/2009/08/css-3-progress/ */
 
.hbox {
	display: -webkit-box;
	-webkit-box-orient: horizontal;
	-webkit-box-align: stretch;
 
	display: -moz-box;
	-moz-box-orient: horizontal;
	-moz-box-align: stretch;
 
	display: box;
	box-orient: horizontal;
	box-align: stretch;
}
 
.hbox > * {
	-webkit-box-flex: 0;
	-moz-box-flex: 0;
	box-flex: 0;
}
 
.vbox {
	display: -webkit-box;
	-webkit-box-orient: vertical;
	-webkit-box-align: stretch;
 
	display: -moz-box;
	-moz-box-orient: vertical;
	-moz-box-align: stretch;
 
	display: box;
	box-orient: vertical;
	box-align: stretch;
}
 
.vbox > * {
	-webkit-box-flex: 0;
	-moz-box-flex: 0;
	box-flex: 0;
}
  
.reverse {
	-webkit-box-direction: reverse;
	-moz-box-direction: reverse;
	box-direction: reverse;
}
 
.box-flex0 {
	-webkit-box-flex: 0;
	-moz-box-flex: 0;
	box-flex: 0;
}
 
.box-flex1, .box-flex {
	-webkit-box-flex: 1;
	-moz-box-flex: 1;
	box-flex: 1;
}
 
.box-flex2 {
	-webkit-box-flex: 2;
	-moz-box-flex: 2;
	box-flex: 2;
}
 
.box-group1 {
	-webkit-box-flex-group: 1;
	-moz-box-flex-group: 1;
	box-flex-group: 1;
}
 
.box-group2 {
	-webkit-box-flex-group: 2;
	-moz-box-flex-group: 2;
	box-flex-group: 2;
}
 
.start {
	-webkit-box-pack: start;
	-moz-box-pack: start;
	box-pack: start;
}
 
.end {
	-webkit-box-pack: end;
	-moz-box-pack: end;
	box-pack: end;
}
 
.center {
	-webkit-box-pack: center;
	-moz-box-pack: center;
	box-pack: center;
}

#message {
    border: 1px solid red;
    background-color: #FFD3D1;
    text-align: center;
    padding: 0.5em;
    margin: 0.5em;
}

#content_panel {
    margin: 0.5em;
}