function checkforminfox(){
  if (document.frm_searchinfo.keyword.value==""){
      alert("请输入关键字!");
      document.frm_searchinfo.keyword.focus();
      return false;
      }
  else
      return true;
}

str="<table width=98% border=0 align=center cellpadding=0 cellspacing=0><form name=frm_searchinfo method=post action=/info/searchin.asp onsubmit='javascript:return checkforminfox();'><tr><td align=center>关键字: <input name=keyword class=p9 size=62>&nbsp;&nbsp;<input type=submit value=搜索 name=Submit class=p9 hidefocus >&nbsp;&nbsp;<font face=Webdings color=#C0C0C0>4</font><a href=/info/searchinfo.asp>高级搜索</a></td></tr></form></table>"

document.write(str)