Introduction

First, there are many solutions, proposed in other posts. I think this one is currently (in 2013) the one which can be compatible with the largest number of browsers, because it doesn’t need any CSS3 properties. However, the method will not work on browsers which doesn’t support contentdeditable, be careful.

Solution with a div contenteditable

As proposed by @Getz, you can use a div with contenteditable and then shape it with some div on it. Here is an example, with two blocks which float at the upper left and the upper right of the main div:

As you can see, you have to play a little with the borders if you want the same result as you requested in your post. The main div has the blue border on every side. Next, red blocks has to be sticked to hide top borders of the main div, and you need to apply border to them only on particular sides (bottom and left for the right block, bottom and right for the left).

After that, you can get the content via Javascript, when the “Submit” button is triggered for example. And I think you can also handle the rest of the CSS (font-size, color, etc.) 🙂

Full code sample

.block_left {
  background-color: red;
  height: 70px;
  width: 100px;
  float: left;
  border-right: 2px solid blue;
  border-bottom: 2px solid blue;
}

.block_right {
  background-color: red;
  height: 70px;
  width: 100px;
  float: right;
  border-left: 2px solid blue;
  border-bottom: 2px solid blue;
}

.div2 {
  background-color: white;
  font-size: 1.5em;
  border: 2px solid blue;
}

.parent {
  height: 300px;
  width: 500px;
}

<div class="parent">
  <div class="block_left"></div>
  <div class="block_right"></div>
  <div class="div2" contenteditable="true">
    "Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut..."
  </div>
</div>