CSS - Style the title from the image tag

CSS - Style the title from the image tag

im trying to style the title from the image tag.
i have search other question but can´t it put working in my project.
but i can´t make any changes.
someone can give me hand with this pls?
my code:
<table class="tablesorter" style="width:98% !important">
<thead>
<tr>
<th>
.....
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
..........
</td>
<td>
<a href="@Url.Action("Edit","Account", new { id=item.UserId })"><img
src="~/Content/images/icon_edit.png" title="Edit"/></a>
</td>
</tr>
</tbody>
<tfooter>
</tfooter>
</table>
CSS:
table.tablesorter tbody tr td a:hover img[title]:after {
content: attr(title);
padding: 4px 8px;
color: #FFF;
background-color:black;
}