This should do it:
<!-- logo -->
<a name="top"></a>
<table border="0" height="123px" width="$stylevar[outertablewidth]" cellpadding="0" cellspacing="0" align="center">
<tr>
<td><img src="images/impact/gradients/left_head.png" border="0" alt="$vboptions[bbtitle]" /></td><td class="head_top" width="100%" align="$stylevar[left]"><a href="$vboptions[bburl]/$vboptions[forumhome].php$session[sessionurl_q]"><img src="$stylevar[titleimage]" border="0" alt="$vboptions[bbtitle]" /></a></td>
<if condition="$show['member']">
<td class="head_top" nowrap="nowrap">
<div class="smallfont" style="background-image: url(images/impact/gradients/pm_back.gif); border: 1px solid #FFFFFF; padding: 15px 15px 15px 15px;">
<strong><phrase 1="$bbuserinfo[username]" 2="member.php?$session[sessionurl]u=$bbuserinfo[userid]">$vbphrase[welcome_x_link_y]</phrase></strong><br />
<phrase 1="$pmbox[lastvisitdate]" 2="$pmbox[lastvisittime]">$vbphrase[last_visited_x_at_y]</phrase>
<if condition="$show['notifications'] AND $show['popups']">
<div><span id="notifications"><a href="usercp.php$session[sessionurl_q]">$vbphrase[your_notifications]:</a> <strong>$notifications_total</strong></span></div>
<script type="text/javascript"> vBmenu.register("notifications"); </script>
<else /><if condition="$show['pmstats']">
<div><phrase 1="$vbphrase[unread_x_nav_compiled]" 2="$vbphrase[total_x_nav_compiled]" 3="$session[sessionurl_q]">$vbphrase[private_messages_nav]</phrase></div>
</if></if>
<if condition="$show['pmwarning']"><div><strong><phrase 1="$vbphrase[pmpercent_nav_compiled]">$vbphrase[your_pm_box_is_x_full]</phrase></strong></div></if>
</div>
</td>
<else />
<td class="head_top" nowrap="nowrap" style="padding:0px">
<div class="smallfont" style="background-image: url(images/impact/gradients/pm_back.gif); border: 1px solid #FFFFFF; padding: 15px 15px 15px 15px;">
<!-- login form -->
<form action="login.php?do=login" method="post" onsubmit="md5hash(vb_login_password, vb_login_md5password, vb_login_md5password_utf, $show[nopasswordempty])">
<script type="text/javascript" src="clientscript/vbulletin_md5.js?v=$vboptions[simpleversion]"></script>
<table cellpadding="0" cellspacing="$stylevar[formspacer]" border="0">
<tr>
<td class="smallfont" style="white-space: nowrap;"><label for="navbar_username">$vbphrase[username]</label></td>
<td><input type="text" class="bginput" style="font-size: 11px" name="vb_login_username" id="navbar_username" size="10" accesskey="u" tabindex="101" value="$vbphrase[username]" onfocus="if (this.value == '$vbphrase[username]') this.value = '';" /></td>
<td class="smallfont" nowrap="nowrap"><label for="cb_cookieuser_navbar"><input type="checkbox" name="cookieuser" value="1" tabindex="103" id="cb_cookieuser_navbar" accesskey="c" />$vbphrase[remember_me]</label></td>
</tr>
<tr>
<td class="smallfont"><label for="navbar_password">$vbphrase[password]</label></td>
<td><input type="password" class="bginput" style="font-size: 11px" name="vb_login_password" id="navbar_password" size="10" tabindex="102" /></td>
<td><input type="submit" class="button" value="$vbphrase[log_in]" tabindex="104" title="$vbphrase[enter_username_to_login_or_register]" accesskey="s" /></td>
</tr>
</table>
<input type="hidden" name="s" value="$session[sessionhash]" />
<input type="hidden" name="securitytoken" value="$bbuserinfo[securitytoken]" />
<input type="hidden" name="do" value="login" />
<input type="hidden" name="vb_login_md5password" />
<input type="hidden" name="vb_login_md5password_utf" />
</form>
<!-- / login form -->
</div>
</td>
</if>
<td class="head_top" align="$stylevar[right]" id="header_right_cell">
<if condition="$ad_location['ad_header_logo']">$ad_location[ad_header_logo]<else /> </if>
</td><td><img src="images/impact/gradients/right_head.png" border="0" alt="$vboptions[bbtitle]" /></td>
</tr>
</table>
<!-- /logo -->
<table border="0" width="$stylevar[outertablewidth]" cellpadding="0" cellspacing="0" align="center">
<tr>
<td>
<!-- nav buttons bar -->
<div style="padding:$stylevar[cellspacing]px; border-left: 3px solid #FFFFFF; border-right: 3px solid #FFFFFF;">
<table cellpadding="0" height="30px" cellspacing="0" border="0" width="100%" align="center">
<tr align="center">
<if condition="$show['member']">
<td class="vbmenu_control"><a href="usercp.php$session[sessionurl_q]">$vbphrase[user_cp]</a></td>
</if>
<if condition="$show['registerbutton']">
<td class="vbmenu_control"><a href="register.php$session[sessionurl_q]" rel="nofollow">$vbphrase[register]</a></td>
</if>
$template_hook[navbar_buttons_left]
<td class="vbmenu_control"><a href="faq.php$session[sessionurl_q]" accesskey="5">$vbphrase[faq]</a></td>
<if condition="$vboptions['enablememberlist']">
<td class="vbmenu_control"><a href="memberlist.php$session[sessionurl_q]">$vbphrase[members_list]</a></td>
</if>
<td class="vbmenu_control"><a href="payments.php">VIP</a></td>
</if>
<td class="vbmenu_control"><a href="calendar.php$session[sessionurl_q]">$vbphrase[calendar]</a></td>
<td class="vbmenu_control"><a href="arcade.php?$session[sessionurl_q]">Arcade</a></td>
<if condition="$show['popups']">
<if condition="$show['searchbuttons']">
<if condition="$show['member']">
<td class="vbmenu_control"><a href="search.php?$session[sessionurl]do=getnew" accesskey="2">$vbphrase[new_posts_nav]</a></td>
<else />
<td class="vbmenu_control"><a href="search.php?$session[sessionurl]do=getdaily" accesskey="2">$vbphrase[todays_posts]</a></td>
</if>
<td id="navbar_search" class="vbmenu_control"><a href="search.php$session[sessionurl_q]" accesskey="4" rel="nofollow">$vbphrase[search]</a> <if condition="$show['quicksearch']"><script type="text/javascript"> vbmenu_register("navbar_search"); </script></if></td>
</if>
<if condition="$show['member']">
<td id="usercptools" class="vbmenu_control"><a href="$show[nojs_link]#usercptools" accesskey="3">$vbphrase[quick_links]</a> <script type="text/javascript"> vbmenu_register("usercptools"); </script></td>
</if>
<else />
<if condition="$show['searchbuttons']">
<td class="vbmenu_control"><a href="search.php$session[sessionurl_q]" accesskey="4">$vbphrase[search]</a></td>
<if condition="$show['member']">
<td class="vbmenu_control"><a href="search.php?$session[sessionurl]do=getnew" accesskey="2">$vbphrase[new_posts_nav]</a></td>
<else />
<td class="vbmenu_control"><a href="search.php?$session[sessionurl]do=getdaily" accesskey="2">$vbphrase[todays_posts]</a></td>
</if>
</if>
<td class="vbmenu_control"><a href="forumdisplay.php?$session[sessionurl]do=markread" rel="nofollow">$vbphrase[mark_forums_read]</a></td>
<if condition="$show['member']">
<td class="vbmenu_control"><a href="#" onclick="window.open('misc.php?$session[sessionurl]do=buddylist&focus=1','buddylist','statusbar=no,me nubar=no,toolbar=no,scrollbars=yes,resizable=yes,w idth=250,height=300'); return false;">$vbphrase[open_contacts]</a></td>
</if>
</if>
$template_hook[navbar_buttons_right]
<if condition="$show['member']">
<td class="vbmenu_control"><a href="login.php?$session[sessionurl]do=logout&logouthash=$bbuserinfo[logouthash]" onclick="return log_out('$vbphrase[sure_you_want_to_log_out]')">$vbphrase[log_out]</a></td>
</if>
</tr>
</table>
</div><div class="dcc"><div class="dcg"></div><div class="dcd"></div></div>
<!-- / nav buttons bar -->
</td>
</tr></table>
<!-- content table -->
$spacer_open
$_phpinclude_output
$ad_location[ad_header_end]
I get this error message unfortunately;
The following error occurred when attempting to evaluate the template 'header':
The conditional on line 87 appears to be missing its beginning tag (<if>). This may cause unexpected behavior.
This is likely caused by a malformed conditional statement.