a[href$=".xls"], a[href$=".xlsx"]{
  display: inline-block;
  padding-right: 20px;
  background: url(../img/icon_excel.png) no-repeat right center;
}
a[href$=".pdf"]{
  display: inline-block;
  padding-right: 20px;
  background: url(../img/icon_pdf.png) no-repeat right center;
}

a[href$=".doc"], a[href$=".docx"]{
  display: inline-block;
  padding-right: 20px;
  background: url(../img/icon_word.png) no-repeat right center;
}