[Seven Skins]

Where are you trying to put this code?
Is it FORUMHOME template?
If it is then find:

<if condition="$show['guest']">
<!-- guest welcome message -->
<table class="tborder" cellpadding="$stylevar[cellpadding]" cellspacing="$stylevar[cellspacing]" border="0" width="100%" align="center">
<tr>
	<td class="tcat"><phrase 1="$vboptions[bbtitle]">$vbphrase[welcome_to_the_x]</phrase></td>
</tr>
<tr>
	<td class="alt1">
		<phrase 1="faq.php$session[sessionurl_q]" 2="register.php$session[sessionurl_q]">$vbphrase[first_visit_message]</phrase>
	</td>
</tr>
</table>
<!-- / guest welcome message -->
<br />
</if>

Replace it with:

<if condition="$show['guest']">
<!-- guest welcome message -->
<table class="tborder" cellpadding="$stylevar[cellpadding]" cellspacing="$stylevar[cellspacing]" border="0" width="100%" align="center">
<tr>
	<td class="tcat"><phrase 1="$vboptions[bbtitle]">$vbphrase[welcome_to_the_x]</phrase></td>
</tr>
<tr>
	<td class="alt1">
		<phrase 1="faq.php$session[sessionurl_q]" 2="register.php$session[sessionurl_q]">$vbphrase[first_visit_message]</phrase>
	</td>
</tr>
    <tr>
        <td class="tcat">Our Sponsor</td>
    </tr>
    <tr>
    <td class="alt1">
<script type="text/javascript"><!--
google_ad_client = "pub-6167630399546150";
/* Study Genie 728x90 */
google_ad_slot = "9845637111";
google_ad_width = 728;
google_ad_height = 90;
//-->
</script>
<script type="text/javascript" src="http://pagead2.googlesyndication.com/pagead/show_ads.js"></script>
        </td>
    </tr>
</table>
<!-- / guest welcome message -->
<br />
</if>