display: inline-block not working unless first div floated:left - html

Question

I am a relative novice in the world of CSS so please excuse my ignorance! I am attempting to use the following CSS to align two divs horizontally:
.portrait {
position: relative;
display:inline-block;
width: 150px;
height: 200px;
padding: 20px 5px 20px 5px;
}
.portraitDetails {
position: relative;
display:inline-block;
width: 830px;
height: 200px;
padding: 20px 5px 20px 5px;
}
Unfortunately, unless I remove the display: inline-block from the .portrait class and replace it with float:left the .portraitDetails div block appears underneath the first div block. What on earth is going on?

Answer 1

Since you provided a working example, the problem seems to be more clear now.
What you have to do is simply remove display: inline-block and width: 830px properties from the right div. Of course remember to NOT add the float property to it.
People sometimes forget what is the purpose of the float property. In your case it is the image which should have float property and the image only. The right div will remain 100% wide by default while the image will float it from the left.
HINT: If the text from the div is long enough to float underneath the image and you want to keep it "indented" at the same point then add the margin to the div with a value equal to the image's width.

Answer 2

The problem with display: inline-block; is that the siblings having this property are always separated by a single white-space but only if there are any white-spaces between their opening and closing tags.
If the parent container has fixed width equal to the sum of the widths of these two divs, then they won't fit because this tiny white-space pushes the second div to the next line. You have to remove the white-space between the tags.
So, instead of that:
<div class="portrait">
...
</div>
<div class="portraitDetails">
...
</div>
you have to do that:
<div class="portrait">
...
</div><div class="portraitDetails"> <!-- NO SPACE between those two -->
...
</div>