Question

I am trying to make an arrow overlap onto the div below it (the way the gray arrow overlaps onto the red on http://tinyletter.com).

Here is the code I am currently using:

#box_1 {
height: 550px;
width: 100%;
font-size: 4.5em;
font-weight: 600;
float: center;
text-align: center;
background-color: #ededed;
padding: 55px 0 0 0;
}

.arrow-down {
width: 0;
height: 0;
border-left: 50px solid transparent;
border-right: 50px solid transparent;
border-top: 50px solid #ededed;
margin-left:auto;
margin-right:auto;
}

#box_2 {
height: 600px;
width: 100%;
font-size: 7em;
float: center;
text-align: center;
background-color: #ed2227;
}

Answer 1

If you’re able to rely upon use of the ::after (or ::before) pseudo-elements, then this is relatively easy simply using borders:

#top {
    position: relative;
    background-color: #ccc;
}

#top::after {
    position: absolute;
    content: '';
    top: 100%;
    left: 50%;
    margin: 0 0 0 -1em;
    border: 1em solid transparent;
    border-top: 1em solid #ccc;
}

JS Fiddle demo.