Are you using Selenium IDE? This is a Firefox plugin to help you create interface test for your web project. If you use Javascript or Ajax, and want to see the result of an interaction, you sometimes need to simulate pressing the ENTER key.
If your code acts upon releasing the enter key, this might help you:
<tr>
<td>keyUp</td>
<td>css=div.yourclass</td>
<td>\13</td>
</tr>
Does your web project do something upon pressing in the enter key? Then try this:
<tr>
<td>keyDown</td>
<td>css=div.yourclass</td>
<td>\13</td>
</tr>