I have an element with a 70% width, and it is floating beside an element with 30% width, but when I add 25px of padding it expands the element and breaks the format, is there any way to make it just increase the contents distance from the edge as opposed to just making it bigger?
When you use the border-box model, the padding is included in the box size. See here for details.
<!DOCTYPE html>
<html>
<head>
<title>padding example</title>
<style type="text/css">
.seventy {
display: block;
float: left;
width: 70%;
background-color: red;
}
.thirty {
display: block;
float: left;
width: 30%;
padding: 25px;
box-sizing: border-box;
-webkit-box-sizing: border-box;
-moz-box-sizing: border-box;
background-color: green;
}
</style>
</head>
<body>
<div class="seventy">Stuff</div>
<div class="thirty">More Stuff</div>
</body>
</html>
I would create another element of the same type (may I guess it's a div?) inside the element and set that one to have a padding/margin of 25px.
For example:
<div id="wrapper">
<div id="width30">
</div>
<div id="width70">
<div id="padding25">
Acctual content here.
</div>
</div>
</div>
</div>
来源：https://stackoverflow.com/questions/5175268/keep-padding-from-making-the-element-bigger