CSS style modification in IFRAME

How to Control CSS in IFRAME outside IFRAME?

 <!  Doctype HTML public "-// W3C // dtd xhtml 1.0 transitional // en" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"  > 
 <  Html  Xmlns  = "Http://www.w3.org/1999/xhtml"  Lang  = "ZH-CN"  > 
 <  Head  > 
<  Meta  HTTP-equiv  = "Content-Type"  Content  = "Text/html; charset = gb2312"  /> 
 <  Title  > </  Title  > 
 </  Head  > 
 < Body  > 
 <  IFRAME  ID  = "FF"  SRC  = "B .htm"  > </  IFRAME  > 
 <  Input  Type  = "Submit"  Value  = "OK" Onclick  = "OK ()"  /> 

 <  Script  Language  = "JavaScript"  >  
  Function  OK ()
{
  //  Operate CSS in IFRAME 
  VaR  IFRAME  =  Document. getelementbyidx (  '  FF  '  );
  VaR  Body  = Iframe.contentdomaindoc ument. Body;

Body. style. margintop  =  50  ;
Body. style. padding  =  0  ;
Body. style. fontsize  =  30  ;
Body. style. textalign =  '  Center  '  ;
Body. style. backgroundcolor  =  '  Red  '  ;
Body. style. Color  = '  Blue  '  ;
}
  </  Script  > 
 </  Body  > 
 </  Html  > 

This is feasible, provided that the IFRAME is in the same domain as your page. If var IFRAME = Document. getelementbyid ('ff ') is cross-domain, the error "no access permission" is returned ".

the question is how to modify the style in the IFRAME for cross-origin .. To be resolved ..