Overflow-x not working
Once you've floated the elements, you've taken them out the document flow and it won't be calculated in the parent's width. You have to use a combination of display: inline-block
on the items instead of float, and then use white-space: nowrap
on the parent.
#testDiv{
width: 400px;
overflow-x: auto;
border:1px solid black;
white-space: nowrap;
font-size: 0;
}
.testimgdiv{
width: 120px;
height: 100px;
display: inline-block;
}
Fiddle
Note: I'm using font-size: 0
to make the items appear right next to each other.
UPDATE
As this post is quite old, it's probably worth noting that this can be done with less code using flexbox (depending on the browser support level required):
#testDiv {
width: 400px;
display: flex;
overflow-x: auto;
}
.testimgdiv {
width: 120px;
height: 100px;
flex: 0 0 auto;
}
<div id="testDiv">
<div class='testimgdiv'>
<img class="testimg" src="https://picsum.photos/100/100/" />
</div>
<div class='testimgdiv'>
<img class="testimg" src="https://picsum.photos/100/100/" />
</div>
<div class='testimgdiv'>
<img class="testimg" src="https://picsum.photos/100/100/" />
</div>
<div class='testimgdiv'>
<img class="testimg" src="https://picsum.photos/100/100/" />
</div>
<div class='testimgdiv'>
<img class="testimg" src="https://picsum.photos/100/100/" />
</div>
<div class='testimgdiv'>
<img class="testimg" src="https://picsum.photos/100/100/" />
</div>
</div>