I have the following page that is a js contact lookup.  It works find when showheader="true" but wont work when set to false.  alsot the image disappears. 

<apex:page showHeader="false">
    
     <input type="hidden" name="testlookup_lkid" id="testlookup_lkid" value="000000000000000" />
<input type="hidden" name="testlookup_lkold" id="testlookup_lkold" value="" />
<input type="hidden" name="testlookup_lktp" id="testlookup_lktp" value="003" />   
<input type="hidden" name="testlookup_lspf" id="testlookup_lspf" value="1" />               
<input type="hidden" name="testlookup_lspfsub" id="testlookup_lspfsub" value="0" />  
<input type="hidden" name="testlookup_mod" id="testlookup_mod" value="0" />   
<span class="lookupInput"> 
<input autocomplete="off" id="testlookup" maxlength="255" name="testlookup" onchange="getElementByIdCS('testlookup_lkid').value='';getElementByIdCS('testlookup_mod').value='1';" size="20" tabindex="4" type="text" value="a" /> 
<a href="javascript:%20openLookup%28%27%2F_ui%2Fcommon%2Fdata%2FLookupPage%3Flkfm%3DeditPage%26lknm%3Dtestlookup%26lktp%3D%27%20%2B%20getElementByIdCS%28%27testlookup_lktp%27%29.value%2C670%2C%271%27%2C%27%26lksrch%3D%27%20%2B%20escapeUTF%28getElementByIdCS%28%27testlookup%27%29.value.substring%280%2C%2080%29%29%29"
   id="con4_lkwgt" onclick="setLastMousePosition(event)" tabindex="4" title="Customer Name Lookup (New Window)">     look
<img src="/s.gif" alt="Customer Name Lookup (New Window)" class="lookupIcon" onblur="this.className = 'lookupIcon';" onfocus="this.className = 'lookupIconOn';" 
     onmouseout="this.className = 'lookupIcon';this.className = 'lookupIcon';" onmouseover="this.className = 'lookupIconOn';this.className = 'lookupIconOn';" 
     title="Customer Name Lookup (New Window)" />
</a>
    </span>
  
    </apex:page>