I have a VF page using the Contenttype set to application/vnd.ms-excel.  The file opens correctly using Excel 2010 but I receive an "Unable to Read File" using Excel 2002.  Different users have different versions of Excel.  I have some older versions of this same VF page Excel files and Excel 2002 can open those files.  The newer version of the VF page has row color coding (partial code below).  Are there any HTML limitations using older versions of Excel causing the file not being able to be read?

 <apex:repeat value="{!wOList}" var="o">
 <apex:variable value="{!cnt+1}" var="cnt"/>
            
   <tr class="{!IF(mod(cnt,2) == 0,'OppEven','OppOdd')}"> 
            
     <!-- LIGHT GREEN -->
       <td style=" background-color: {!IF(mod(cnt,2) == 0,'lightgreen','')}; color: black;">
         <apex:outputText value="Opportunity"/>
       </td>
       <td style="background-color: {!IF(mod(cnt,2) == 0,'lightgreen','')}; color: black;">
          <apex:outputField value="{!o.o.District__c}"/>
       </td>

     <!-- LIGHT BLUE -->               
        <td style="background-color: {!IF(mod(cnt,2) == 0,'lightblue','')}; color: black;">
          <apex:outputLink value="/{!o.o.id}">{!o.o.Opportunity_Number__c}</apex:outputLink>
        </td>