About error-code 404 is called for each struts action class

[Emi]

Hello,

In web.xml:
   <error-page>
      <error-code>404</error-code>
<location>/WEB-INF/pages/errorinfo/tiles_404.jsp</location>
   </error-page>

For each struts2 action class shows/direct to correct page, but the 
above line is always called.

Could someone let me know what may cause the above section called please?

Thanks a lot!
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struts2.5.14.1, tiles3.0.8, servlet2.4