Whenever I click on "History" or "AI scripting" the unordered list would have to dissapear as you see from my code. But when clicking on any of them I get an error "Object expected" (line 79).

Could anyone enlighten me ?

Code:
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	{
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		var objweb_+_community_development = document.getElementById("navItemweb_+_community_development");
var objartificial_intelligence_scripting = document.getElementById("navItemartificial_intelligence_scripting");
var objgame_design = document.getElementById("navItemgame_design");
var objgraphic_art = document.getElementById("navItemgraphic_art");
var objhistory = document.getElementById("navItemhistory");
var objprogramming = document.getElementById("navItemprogramming");
var objrandom_map_scripting = document.getElementById("navItemrandom_map_scripting");
var objscenario_design = document.getElementById("navItemscenario_design");
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if( choice == "openhistory" ) objhistory.style.display = "block";
if( choice == "openprogramming" ) objprogramming.style.display = "block";
if( choice == "openrandom_map_scripting" ) objrandom_map_scripting.style.display = "block";
if( choice == "openscenario_design" ) objscenario_design.style.display = "block";
if( choice == "opensound" ) objsound.style.display = "block";

		if( choice == "closeweb_+_community_development" ) objweb_+_community_development.style.display = "none";
if( choice == "closeartificial_intelligence_scripting" ) objartificial_intelligence_scripting.style.display = "none";
if( choice == "closegame_design" ) objgame_design.style.display = "none";
if( choice == "closegraphic_art" ) objgraphic_art.style.display = "none";
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<h2>Welcome back</h2>
<p><b><span style='color:#c00'>DarkAngelBGE</span></b></p>
<p>0.A.D. Web + Community Development Department Leader</p>
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<h2>Departments</h2><h3><a href="#" onclick="mirage('closeweb_+_community_development')"><b><span style='color:#c00'>Web + Community Development</span></b></a></h3><ul id="navItemweb_+_community_development" class="secbg"><li><a href="http://localhost/wildfire_games/intranet/index.php?act=task&amp;code=01&amp;deptId=8">New Task</a></li><li><a href="http://localhost/wildfire_games/intranet/index.php?act=task&amp;code=02&amp;deptId=8">View Tasks</a></li><li><a href="http://localhost/wildfire_games/intranet/index.php?act=memberlist&amp;code=01&amp;deptId=8">Memberlist</a></li></ul><h3><a href="#" onclick="mirage('closeartificial_intelligence_scripting')">Artificial Intelligence Scripting</a></h3><ul id="navItemartificial_intelligence_scripting"><li><a href="http://localhost/wildfire_games/intranet/index.php?act=task&amp;code=01&amp;deptId=6">New Task</a></li><li><a href="http://localhost/wildfire_games/intranet/index.php?act=task&amp;code=02&amp;deptId=6">View Tasks</a></li><li><a href="http://localhost/wildfire_games/intranet/index.php?act=memberlist&amp;code=01&amp;deptId=6">Memberlist</a></li></ul><h3><a href="#" onclick="mirage('closegame_design')">Game Design</a></h3><ul id="navItemgame_design"><li><a href="http://localhost/wildfire_games/intranet/index.php?act=task&amp;code=01&amp;deptId=1">New Task</a></li><li><a href="http://localhost/wildfire_games/intranet/index.php?act=task&amp;code=02&amp;deptId=1">View Tasks</a></li><li><a href="http://localhost/wildfire_games/intranet/index.php?act=memberlist&amp;code=01&amp;deptId=1">Memberlist</a></li></ul><h3><a href="#" onclick="mirage('closegraphic_art')">Graphic Art</a></h3><ul id="navItemgraphic_art"><li><a href="http://localhost/wildfire_games/intranet/index.php?act=task&amp;code=01&amp;deptId=7">New Task</a></li><li><a href="http://localhost/wildfire_games/intranet/index.php?act=task&amp;code=02&amp;deptId=7">View Tasks</a></li><li><a href="http://localhost/wildfire_games/intranet/index.php?act=memberlist&amp;code=01&amp;deptId=7">Memberlist</a></li></ul><h3><a href="#" onclick="mirage('closehistory')">History</a></h3><ul id="navItemhistory"><li><a href="http://localhost/wildfire_games/intranet/index.php?act=task&amp;code=01&amp;deptId=25">New Task</a></li><li><a href="http://localhost/wildfire_games/intranet/index.php?act=task&amp;code=02&amp;deptId=25">View Tasks</a></li><li><a href="http://localhost/wildfire_games/intranet/index.php?act=memberlist&amp;code=01&amp;deptId=25">Memberlist</a></li></ul><h3><a href="#" onclick="mirage('closeprogramming')">Programming</a></h3><ul id="navItemprogramming"><li><a href="http://localhost/wildfire_games/intranet/index.php?act=task&amp;code=01&amp;deptId=3">New Task</a></li><li><a href="http://localhost/wildfire_games/intranet/index.php?act=task&amp;code=02&amp;deptId=3">View Tasks</a></li><li><a href="http://localhost/wildfire_games/intranet/index.php?act=memberlist&amp;code=01&amp;deptId=3">Memberlist</a></li></ul><h3><a href="#" onclick="mirage('closerandom_map_scripting')">Random Map Scripting</a></h3><ul id="navItemrandom_map_scripting"><li><a href="http://localhost/wildfire_games/intranet/index.php?act=task&amp;code=01&amp;deptId=5">New Task</a></li><li><a href="http://localhost/wildfire_games/intranet/index.php?act=task&amp;code=02&amp;deptId=5">View Tasks</a></li><li><a href="http://localhost/wildfire_games/intranet/index.php?act=memberlist&amp;code=01&amp;deptId=5">Memberlist</a></li></ul><h3><a href="#" onclick="mirage('closescenario_design')">Scenario Design</a></h3><ul id="navItemscenario_design"><li><a href="http://localhost/wildfire_games/intranet/index.php?act=task&amp;code=01&amp;deptId=2">New Task</a></li><li><a href="http://localhost/wildfire_games/intranet/index.php?act=task&amp;code=02&amp;deptId=2">View Tasks</a></li><li><a href="http://localhost/wildfire_games/intranet/index.php?act=memberlist&amp;code=01&amp;deptId=2">Memberlist</a></li></ul><h3><a href="#" onclick="mirage('closesound')">Sound</a></h3><ul id="navItemsound"><li><a href="http://localhost/wildfire_games/intranet/index.php?act=task&amp;code=01&amp;deptId=4">New Task</a></li><li><a href="http://localhost/wildfire_games/intranet/index.php?act=task&amp;code=02&amp;deptId=4">View Tasks</a></li><li><a href="http://localhost/wildfire_games/intranet/index.php?act=memberlist&amp;code=01&amp;deptId=4">Memberlist</a></li></ul></div><div>
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<h2><span>View Members - Graphic Art Department</span></h2>
<div class="contentbar"></div><p>Total Department Members: <b>10</b></p><table><tr>
<td width="25%"><div class="table_top_row">Name</div></td>
<td width="25%"><div class="table_top_row">Project/Rank</div></td>
<td width="30%"><div class="table_top_row">Department</div></td>
<td width="5%"><div class="table_top_row">Absence</div></td>
<td width="5%"><div class="table_top_row">Edit</div></td><tr><td><a href="http://forums.wildfiregames.com/wfg/index.php?act=Msg&amp;CODE=4&amp;MID=3"><b><span style='color:red'>Wijitmaker</span></b></a></td>
<td><b><span style='color:red'>0.A.D. Project Leader</span></b></td>
<td>Graphic Art</td>
<td>no</td>
<td></tr><tr><td><a href="http://forums.wildfiregames.com/wfg/index.php?act=Msg&amp;CODE=4&amp;MID=5"><b><span style='color:#9898FF'>Fire Giant</span></b></a></td>
<td><b><span style='color:#9898FF'>0.A.D. Staff Member</span></b></td>
<td>Graphic Art</td>
<td>no</td>
<td></tr><tr><td><a href="http://forums.wildfiregames.com/wfg/index.php?act=Msg&amp;CODE=4&amp;MID=24"><b><span style='color:#9898FF'>irishstag</span></b></a></td>
<td><b><span style='color:#9898FF'>0.A.D. Staff Member</span></b></td>
<td>Graphic Art</td>
<td>no</td>
<td></tr><tr><td><a href="http://forums.wildfiregames.com/wfg/index.php?act=Msg&amp;CODE=4&amp;MID=17"><b><span style='color:#9898FF'>Jeru</span></b></a></td>
<td><b><span style='color:#9898FF'>0.A.D. Staff Member</span></b></td>
<td>Graphic Art</td>
<td>no</td>
<td></tr><tr><td><a href="http://forums.wildfiregames.com/wfg/index.php?act=Msg&amp;CODE=4&amp;MID=130"><b><span style='color:#9898FF'>Mythos_Ruler</span></b></a></td>
<td><b><span style='color:#9898FF'>0.A.D. Staff Member</span></b></td>
<td>Graphic Art</td>
<td>no</td>
<td></tr><tr><td><a href="http://forums.wildfiregames.com/wfg/index.php?act=Msg&amp;CODE=4&amp;MID=55"><b><span style='color:#9898FF'>Quacker</span></b></a></td>
<td><b><span style='color:#9898FF'>0.A.D. Staff Member</span></b></td>
<td>Graphic Art</td>
<td>no</td>
<td></tr><tr><td><a href="http://forums.wildfiregames.com/wfg/index.php?act=Msg&amp;CODE=4&amp;MID=62"><b><span style='color:#9898FF'>Render</span></b></a></td>
<td><b><span style='color:#9898FF'>0.A.D. Staff Member</span></b></td>
<td>Graphic Art</td>
<td>no</td>
<td></tr><tr><td><a href="http://forums.wildfiregames.com/wfg/index.php?act=Msg&amp;CODE=4&amp;MID=37"><b><span style='color:#9898FF'>Saurabh</span></b></a></td>
<td><b><span style='color:#9898FF'>0.A.D. Staff Member</span></b></td>
<td>Graphic Art</td>
<td>no</td>
<td></tr><tr><td><a href="http://forums.wildfiregames.com/wfg/index.php?act=Msg&amp;CODE=4&amp;MID=252"><b><span style='color:#9898FF'>Annatar</span></b></a></td>
<td><b><span style='color:#9898FF'>0.A.D. Staff Member</span></b></td>
<td>Graphic Art</td>
<td>no</td>
<td></tr><tr><td><a href="http://forums.wildfiregames.com/wfg/index.php?act=Msg&amp;CODE=4&amp;MID=244"><b><span style='color:#9898FF'>Hyborian</span></b></a></td>
<td><b><span style='color:#9898FF'>0.A.D. Staff Member</span></b></td>
<td>Graphic Art</td>
<td>no</td>
<td></tr></table></div></div>
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