How to collapse the borders of a set of <div> tags using CSS?

Question

I have a grid made of DIV's with a fixed width and a border of 1 px. Now where two DIV's touch each other, the border becomes 2px, obviously.

How can I just get a 1px border in the whole grid?

This is what I mean:

http://jsfiddle.net/Before/4uPtj/

HTML:

<div class="gridcontainer">
  <div class="griditem"></div>
  <!-- 15 more times -->
</div>

CSS:

div.gridcontainer
{
  width: 80px;
  line-height: 0;
}

div.griditem
{
  display: inline-block;            
  border: 1px solid black;
  width: 18px;
  height: 18px;
}

Answer 1

Try this:

div.griditem
{
    display: inline-block;            
    border: 1px solid black;
    width: 18px;
    height: 18px;
    margin-left: -1px;
    margin-bottom: -1px;
}

Answer 2

Hi you define you your gridcontainer with according to your griditem div

as like this

css

   div.gridcontainer
    {
        width: 76px;
        line-height: 0;
        border: solid black;
        border-width: 0 1px 1px 0;
    }

    div.griditem
    {
        display:inline-block;           
        border: solid black;
        border-width: 1px 0 0 1px;
        width: 18px;
        height: 18px;
    }

HTML

<div class="gridcontainer">
    <div class="griditem"></div><div class="griditem"></div><div class="griditem"></div><div class="griditem"></div><div class="griditem"></div><div class="griditem"></div><div class="griditem"></div><div class="griditem"></div><div class="griditem"></div><div class="griditem"></div><div class="griditem"></div><div class="griditem"></div><div class="griditem"></div><div class="griditem"></div><div class="griditem"></div><div class="griditem"></div>
</div>

​Live demo here http://jsfiddle.net/rohitazad/4uPtj/1/

Answer 3

Because of the title probably many ppl will end up here looking for solution for an actual css grid layout problem like myself. For them here's a workaround using a combination of grid-gap and box-shadow

.bar {
    max-width: 200px;
    display: grid;
    grid-template-columns: 1fr 1fr 1fr 1fr;
    grid-gap: 1px;
}
.foo {
  box-shadow: 0 0 0 1px #000;
}

<div class="bar">
    <div class="foo">1</div>
    <div class="foo">2</div>
    <div class="foo">3</div>
    <div class="foo">4</div>
    <div class="foo">5</div>
    <div class="foo">6</div>
    <div class="foo">7</div>
    <div class="foo">8</div>
    <div class="foo">9</div>
</div>