Why does 'clear:left' also clears right?

Question

I've been struggling to get CSS floating to work (in my head).

Note the following example:

<style type="text/css">
    div.container {
        width:500px;
    }
    div.left {
        float:left;
        clear:left;
    }
    div.right {
        float:right;
    }
</style>
<div class="container">
    <div class="left">leftdata 1</div>
    <div class="left">leftdata 2</div>
    <div class="right">rightdata 1</div>
    <div class="right">rightdata 2</div>
    <div class="right">rightdata 3</div>
    <div class="right">rightdata 4</div>
</div>

This will give the following output:

+--------------------------------------------------------------------+
| leftdata 1                                                         |
| leftdata 2         rightdata 1 rightdata 2 rightdata 3 rightdata 4 |
|                                                                    |
+--------------------------------------------------------------------+

However I was expecting this:

+--------------------------------------------------------------------+
| leftdata 1         rightdata 1 rightdata 2 rightdata 3 rightdata 4 |
| leftdata 2                                                         |
|                                                                    |
+--------------------------------------------------------------------+

Why is clear:left; also clearing right?

---

My goal:

I want to only add a clear:right; to the DIVs marked with class: right. This should produce the following:

<style type="text/css">
    div.left {float:left;clear:left;}
    div.right {float:right;clear:right;}
</style>

+--------------------------------------------------------------------+
| leftdata 1                                             rightdata 1 |
| leftdata 2                                             rightdata 2 |
|                                                        rightdata 3 |
|                                                        rightdata 4 |
+--------------------------------------------------------------------+

Answer 1

In your first example the rightdata-divs are placed under the left ones because they appear later in the document. Place them first and you get your expected results.

Or you could try something along the lines of:

<style type="text/css">
  div.left {
    float: left;
  }

  div.right {
    float: right;

  }
  div.container {
    width:500px;
    overflow: auto; /* to make sure .container expands vertically */
  }

<div class="container">
  <div class="left">
    <div>leftdata 1</div>
    <div>leftdata 2</div>
  </div>
  <div class="right">
    <div>rightdata 1</div>
    <div>rightdata 2</div>
    <div>rightdata 3</div>
    <div>rightdata 4</div>
  </div>
</div>