Правильный код:
<style>
.upload input[type='file']{
position: absolute;
float: left;
opacity: 0; /* For IE8 "Keep the IE opacity settings in this order for max compatibility" */
-ms-filter: "progid:DXImageTransform.Microsoft.Alpha(Opacity=0)"; /* For IE5 - 7 */
filter: alpha(opacity=0);
width: 100px; height: 30px; z-index: 51
}
.upload input[type='button']{
width: 100px;
height: 30px;
z-index: 50;
}
.upload input[type='submit']{
display: none;
}
.upload{
width: 100px; height: 30px
}
</style>
<div class="upload">
<input type='file' ID="flArquivo" onchange="upload();" />
<input type="button" value="Selecionar" onchange="open();" />
<input type='submit' ID="btnEnviarImagem" />
</div>
<script type="text/javascript">
function open() {
$('#flArquivo').click();
}
function upload() {
$('#btnEnviarImagem').click();
}
</script>