a[href^="http:"] {
    display:inline-block;
    padding-right:14px;
    background:transparent url(/Images/ExternalLink.gif) center right no-repeat;
    }

    a[href^="mailto:"] {
    display:inline-block;
    padding-left:20px;
    line-height:18px;
    background:transparent url(/Images/MailTo.gif) center left no-repeat;
    }

    a[href$='.pdf'] {
    display:inline-block;
    padding-left:20px;
    line-height:18px;
    background:transparent url(/Images/PDFIcon.gif) center left no-repeat;
    }

    a[href$='.swf'], a[href$='.fla'], a[href$='.swd'] {
    display:inline-block;
    padding-left:20px;
    line-height:18px;
    background:transparent url(/Images/FlashIcon.gif) center left no-repeat;
    }

    a[href$='.xls'], a[href$='.csv'], a[href$='.xlt'], a[href$='.xlw'] {
    display:inline-block;
    padding-left:20px;
    line-height:18px;
    background:transparent url(/Images/ExcelIcon.gif) center left no-repeat;
    }

    a[href$='.ppt'], a[href$='.pps'] {
    display:inline-block;
    padding-left:20px;
    line-height:18px;
    background:transparent url(/Images/PowerPointIcon.gif) center left no-repeat;
    }

    a[href$='.doc'], a[href$='.rtf'], a[href$='.txt'], a[href$='.wps'] {
    display:inline-block;
    padding-left:20px;
    line-height:18px;
    background:transparent url(/Images/WordDocIcon.gif) center left no-repeat;
    }

    a[href$='.zip'], a[href$='.gzip'], a[href$='.rar'] {
    display:inline-block;
    padding-left:20px;
    line-height:18px;
    background:transparent url(/Images/ZIPIcon.gif) center left no-repeat;
    }

file types in CSS

css, file

CSS