Template:Mbox/styles.css

.mbox {
    width: 80%;
    margin: 0 10%; /* Prevent overlap with other elements */
    border-width: 1px 10px;
    border-style: solid;
}
.mbox-small {
	width: 40%;
    border-width: 1px 5px;
    border-style: solid;
	font-size: .85em;
}
.mbox-large {
    width: 100%;
    border-width: 2px 15px;
    border-style: solid;
	font-size: 1.15em;
}

/* Single border between stacked message boxes */
table.mbox + table.mbox {   
    margin-top: -1px;
}
table.mbox-small + table.mbox-small {   
    margin-top: -1px;
}
table.mbox-large + table.mbox-large {   
    margin-top: -2px;
}

/* Mbox text cell */
.mbox-text {
	border: none;
	padding: 0.25em 0.4em;      /* 0.5em left/right */
	width: 100%;                /* Make text cell take up full length of mbox */
	box-sizing: border-box;		/* Fixes padding and width conflict */
}

/* Mbox images */
.mbox-image {
	border: none;
    padding: 2px 4px;
	text-align: center;
}