Why does this line 'jump' when I call slideDown?

Question

Since there's a lot of code, I won't post it here. Rather, you can find it all here. That way you can play around with it and run it:

function P_Expand(item_id) {
  $('#p_' + item_id).slideToggle();
}

.data_table {
  width: 650px;
  margin-left: auto;
  margin-right: auto;
  border-collapse: collapse;
}
.data_table tbody th {
  border-bottom: 1px solid #555;
  text-align: left;
}
.data_table tbody tr td a {
  color: #8b9cb0;
  text-decoration: none;
}
.hidden_data {
  display: none;
  padding: 10px;
  font-style: italic;
  color: #777;
}

<table class='data_table'>
  <tbody>
    <tr>
      <td>
        <a href='javascript:void(0)' onclick='P_Expand(9)'>Drop me down!</a>
      </td>
      <td>...</td>
      <td>...</td>
    </tr>
    <tr>
      <td colspan='3' style='background-color: #eee'>
        <div id='p_9' class='hidden_data'>
          <p style="margin: 0px;">Donec dolor urna, vehicula in elementum eget, auctor dignissim nibh. Morbi et augue et nisi.</p>
        </div>
      </td>
    </tr>
    <tr>
      <td>Line number 2...</td>
      <td>...</td>
      <td>...</td>
    </tr>
  </tbody>
</table>

The problem happens when the 'Drop me down!' link is clicked. The DIV slides down as expected, but makes a sudden 'jump' right at the end.

Why does it do this, and how can I make it go away?

Answer 1

Actually you don't need any of this. Just give your hidden element a width:

.hidden_data {
    display: none;
    padding: 10px;
    font-style: italic;
    color: #777;
    width: 300px;
}

It will just works!

PS: I spent all the weekend on this...

Answer 2

demo

codes link

.hidden_data {
    overflow: hidden;
    display:none; /* <--- remove this */
    padding: 10px;
    font-style: italic;
    color: #777;
}​

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