You need to give action name in url as following
<table width="100%" cellspacing="0" border="0" cellpadding="0">
<tr>
<td colspan="3" align="left"><s:url
action="fileValidate" id="idfileValidate" escapeAmp="false"></s:url> <input
type="button" class="btn"/></td>
</tr>
...............
<tr>
<td colspan="3" align="left"><input type="button" class="btn"/><s:url
action="fileUpload" id="idfileUpload" escapeAmp="false"></s:url> <input
type="button" class="btn" id="buttonUpload"/>
</td>
</tr>
</table>
You need to mapped that action in struts.xml as following
<action name="fileValidate"
class="com.action.struts2.validatefileaction" >
<action name="fileupload"
class="com.action.struts2.fileupload" >
Try this