i add custom css but it is not working?

hi
I have my company site develop on wordpress which i handle . the problem is that i have write custom CSS in style.css and making class in html of this css name but it is not working. i write code here kindly some one help me plz.
CSS code:
p.bottom_border{
border-style:solid;
border-bottom-width: 1px;
border-bottom-style:solid;
border-bottom-color:#FFFFFF;
}
p.bottom_border:hover{
border-style:solid;
border-bottom-width: 1px;
border-bottom-style:solid;
border-bottom-color:#0000FF;
cursor:pointer;
}

HTML code:

<tr bgcolor=”#FFFFFF”>

<td height=”22″ nowrap bgcolor=”#B9CDFE”> <p class=”bottom_border”>Tracking No : </p></td>

<td width=”160″ nowrap bgcolor=”#B9CDFE”><p class=”bottom_border”><? echo (@$row[“cnno”]) ?></p></td>

<td width=”50″ nowrap bgcolor=”#B9CDFE”><p class=”bottom_border”> Booking Date : </p></td>

<td width=”157″ nowrap bgcolor=”#B9CDFE”><p class=”bottom_border”><? echo (@$row[“book_date”]); ?></p></td>
</tr>

i donot write whole html code b/c it is too long.
reply me as soon as possible