есть еще один способ
<div class="inputblock" style="width: 350px;">
<ajaxToolkit:AsyncFileUpload runat="server" ID="FileUP" ClientIDMode="AutoID" UploaderStyle="Modern" OnUploadedComplete="FileUP_UploadedComplete" Width="100%" />
</div>
это выглядит примерно так
<div id="ctl00_PopUpPlaceHolder_FileUP">
<input name="ctl00$PopUpPlaceHolder$FileUP$ctl00" id="ctl00_PopUpPlaceHolder_FileUP_ctl00" type="hidden">
<div id="ctl00_PopUpPlaceHolder_FileUP_ctl01" style='background: url("/WebResource.axd?d=some&pars") no-repeat 100% 1px; margin: 0px; width: 100% !important; height: 24px; text-align: right; min-width: 100%;'>
<input name="ctl00$PopUpPlaceHolder$FileUP$ctl02" id="ctl00_PopUpPlaceHolder_FileUP_ctl02" style="width: 100%; font-size: 14px; opacity: 0; -moz-opacity: 0.0;" type="file">
<div style="text-align: left; margin-top: -23px;" type="text">
<input name="ctl00$PopUpPlaceHolder$FileUP$ctl04" id="ctl00_PopUpPlaceHolder_FileUP_ctl04" style="width: 248px; height: 17px; font-family: Tahoma; font-size: 12px;" type="text" readonly="readonly">
</div>
</div>
, и вы всегда можете изменить th css, чтобы изменить любой syling, как это:
#ctl00_PopUpPlaceHolder_FileUP_ctl01 {
background: url("/img/input_file.png") no-repeat right top !important;
//some othe stylings, but "!important" is strongly necessarily
}
это работает.