Problem with HTML: How do I make the button visible?

Hi Professional HTML-ers!

I have an issue with adding in a autoresponder form raw HTML into the side bar.
Here's the coding:

<form action="http://virtualinternetmarketinglibrary.com/index.php" method="post">
<table style="border-collapse: collapse; padding: 10px;" border="0" cellspacing="0" cellpadding="0" bordercolor="#111111">
<tbody>
<tr>
<td>
<div><strong>Name:</strong>&nbsp;<input name="name" size="20" type="text" /><br /><strong>Email:</strong>&nbsp;<input name="email" size="20" type="text" /><br /><input class="button" name="Add" type="submit" value="Join My Mailing List" /></div>
</td>
</tr>
</tbody>
</table>
<input name="act" type="hidden" value="s_add" /> <input name="listid" type="hidden" value="1" /></form>

Looks good enough? But here is where the problem arise. I inputted the HTML into a HTML-enabled widget, and this is the result: Virtual Internet Marketing Library

Look at the top right section, the one that reads: "Receive Updates!"
That's the problem: The "Add" Icon is INVISIBLE :confused:

Not very sure what's going on and sure could use some advice!

Thanks in advances!

Regards,
Edmund