I have a large DIV of 586px width. Within this are two smaller DIVs, both 266px width.
When I preview the page though, there’s a small margin in between them. I’ve tried troubleshooting this with Inspect Element, but not found any extra margins in the metrics.

The CSS:
#category-results {
width: 586px;
height: 1000px;
background-color: fuchsia;
}
.category-item-full {
height: 158px;
width: 266px;
background-color: green;
position: relative;
display: inline-block;
margin: 0px;
}
The HTML:
<div id="category-results">
<div class="category-item-full">
</div>
<div class="category-item-full">
</div>
</div>
Remove
display: inline-block;in your CSS.Or, if you need it, remove white space between
<div>s in HTML: