Question

I have a box with a triangle that intersects it and I’d like a similar triangle to be cut out from the box so there is a white gap between the two. As this is a little hard to explain I created a jsFiddle here that shows what I have already.

Here is a screenshot

HTML

<div id="alertdetails">
    <h2>UH OH</h2>
    Date: 05/11/2012 15:57:46

    <br><br>
    <a href="">View</a>
</div>
<div id="arrow-right"></div>
​

CSS

#alertdetails {
    background-color: #F8F8F8;
    border: 1px solid #CCCCCC;
    border-radius: 5px 5px 5px 5px;
    left: 25px;
    padding: 20px;
    position: absolute;
    text-shadow: 0 1px #FFFFFF;
    top: 15px;
}

#arrow-right {
    position: absolute;
    top: 45px;
    left: 15px;
    width: 0; 
    height: 0; 
    border-top: 20px solid transparent;
    border-bottom: 20px solid transparent;

    border-left: 20px solid #303030;
}
​

Answer 1

You can do this without the extra DIV for the arrow by using a UTF-8 “right arrow” and the :before pseudo class. This will give you a little more control over the style of the arrow.

#alertdetails {
    background-color: #F8F8F8;
    border: 1px solid #CCCCCC;
    border-radius: 5px 5px 5px 5px;
    left: 25px;
    padding: 20px;
    position: relative;
    margin-top:15px;
    text-shadow: 0 1px #FFFFFF;
}

#alertdetails::before  {
    content:"\25b6";
    position:absolute; 
    top:20px;
    left:-20px;
    font-size:60px;
    color:#ffffff;

}