Why is my content too wide for the container?

Question

All of the widths and margins come out to a total of 99.96%, so it should fit just fine in the 100%. I understand that borders add width, so I've done box-sizing: border-box; but that doesn't seem to fix it. If I float: left then it works okay in Chrome, but I feel like that's a crappy workaround anyway and doesn't actually fix the problem.

Why doesn't it all fit on one line?

Here's my jsfiddle.

HTML

<div id="container">
    <a href="#">
        1
    </a>
    <a href="#">
        2
    </a>
    <a href="#">
        3
    </a>
    <a href="#">
        4
    </a>
</div>

CSS

body {
    border: 1px solid black;
    background-color: #BCCDDC;
    margin: 5% 25%
}

#container a {
    font-family: 'Open Sans', sans-serif;
    text-align: center;
    box-sizing: border-box;
    -webkit-box-sizing: border-box;
    border: 2px solid #fff;
    display: inline-block;
    width: 15%;
    margin: 0 6.66%;
    padding: 20px 0;
}

#container a:first-of-type {
    margin-left: 0 !important;;
}

#container a:last-of-type {
    margin-right: 0 !important;
}

Answer 1

inline-block elements aren't floated; they're inline, which means white space between elements is preserved.

You can fix this by removing the whitespace entirely between <a> tags: http://jsfiddle.net/mblase75/y1Ltq1fc/4/

    <a href="#">
        1
    </a><a href="#">
        2
    </a><a href="#">
        3
    </a><a href="#">
        4
    </a>

---

Alternatively, make the anchors float: left and put overflow: auto on the parent #container: http://jsfiddle.net/mblase75/y1Ltq1fc/9/

#container {
    overflow: auto;
}
#container a {
    float: left; /* automatically sets display:block */
    /* etc. */
}

Here are some other techniques, if you have a problem implementing the above.

Answer 2

display: inline-block; honors whitespace between elements, to fix it you can either:

Remove the whitespace between the elements in the HTML

<div id="container"> 
    <a href="#">1</a><a href="#">2</a><a href="#">3</a><a href="#">4</a>
</div>

http://jsfiddle.net/1sgjh5c3/

Make the font-size zero on the container in CSS

#container {
    font-size: 0;
}
#container a {
    font-size: 12px;
}

http://jsfiddle.net/jLhr8xcn/