+3  A: 

use style="float:left" on each DIV (either directly or via a stylesheet)

James Curran
I assume I would have to make an additional div to contain the date and month then float that correct?
Anders
won't "display: table-cell;" not work in IE through v7?
Matt Dunnam
+1  A: 

float:left if you want block elements to sit next to each other.

qui
A: 
  1. Copy dContainer and place the copy immediately after it.
  2. Change the ID and the new ID to the #dContainer style.
  3. Add a new CSS block that has just #dContainer (not the new div) and put "float:left;" in the block.
Dan Goldstein
+2  A: 
<html>
<head>
<title>Testing some CSS</title>
<style type="text/css">
.dDay {
    font-size:205%
}
.dMon {
    font-weight:bold;
    font-variant:small-caps;
    font-size:130%;
    margin-top:-.7em;
}
.detailContainer {
    vertical-align:middle;
    display:table-cell;
    padding:0em 0em 0em 1em;
}
#dContainer, #dContainer2 {
    border:1px solid green;
    display:table;
    height:3.25em;
    float: left;
    }
</style>
<body>
<div id="dContainer">
    <div class="dDay">31</div>
    <div class="dMon">sep</div>
</div>
<div id="dContainer2">
    <div class="dDay">31</div>
    <div class="dMon">sep</div>
    <div class="detailContainer">Test O.O</div>
</div>
</body>
</html>
Abyss Knight
It would probably be better to make "dContainer" a class and then just resuse it, rather than having seperate id's for it. They do the same thing afterall
qui
Yep, of course. I just put this together in a few seconds to make life easier for the OP in testing. Also, you'll need to issue a clear before any other block or inline level elements, I believe.
Abyss Knight
A: 
<html>
<head>
<title>Testing some CSS</title>
<style type="text/css">
.dDay {
    font-size:205%
}
.dMon {
    font-weight:bold;
    font-variant:small-caps;
    font-size:130%;
    margin-top:-.7em;
}
.dDate {
    display:table-cell;
}
.detailContainer {
    vertical-align:middle;
    display:table-cell;
    padding-left:1em;
}
#dContainer {
    border:1px solid green;
    display:table;
    height:3.25em;
}
</style>
<body>
<div id="dContainer">
    <div class="dDate">
        <div class="dDay">31</div>
        <div class="dMon">sep</div>
    </div>
    <div class="dDate">
        <div class="dDay">31</div>
        <div class="dMon">sep</div>
    </div>
    <div class="detailContainer">Test O.O</div>
</div>
</body>
</html>

[EDIT] Looking at the other answers:
- Float is of course the right answer, I just went with the initial logic, actually finishing it (making a real table might be actually the logical final step...)
- Note: doesn't look nice in IE (6, 7).

PhiLho
A: 

Is there any reason why you can't use <span> tags instead of <div>'s? That way your page would still make sense when read without CSS.

Ian Oxley