the correct css syntax would be:
border-bottom: size style color;
So, in your case:
border-bottom: 1px solid #CCCCCC;
edit: actually, it seems TR doesn't act like it 'contains' the TD elements in IE7. One trick you can do is have the table collapse borders, then apply all TDs under .item_fact to have the border-bottom themselves.
Like this:
<html>
<head>
<style type="text/css">
table {
border-collapse: collapse;
}
.item_fact td {
border-bottom:1px solid #CCCCCC;
}
</style>
</head>
<body>
<table>
<tr class="item_fact">
<td> hello </td>
<td> world </td>
</tr>
</table>
</body>
</html>