<input type="file" accept="image/jpeg,image/png,image/bmp" name="fileName" value="" />

<script type="text/javascript">
	function Validatebodypanelbumper(theForm) {
		var extension = theForm.FileUpload.value
				.substr(theForm.FileUpload1.value.lastIndexOf('.'));
		if ((extension.toLowerCase() != ".gif")
				&& (extension.toLowerCase() != ".jpg") && (extension != "")) {
			alert("The \"FileUpload\" field contains an unapproved filename.");
			theForm.FileUpload1.focus();
			return false;
		}
		return true;
	}
</script>

onsubmit="return Validatebodypanelbumper(this);"

<script type="text/javascript">
	function checkSize(max_img_size) {
		var input = document.getElementById("FileUpload");
		// check for browser support (may need to be modified)
		if (input.files && input.files.length == 1) {
			if (input.files[0].size > max_img_size) {
				alert("The file must be less than "
						+ (max_img_size / 1024 / 1024) + "MB");
				return false;
			}
		}

		return true;
	}
</script>

<form id="theForm" method=post action="FileUploadServlet" 
		enctype="multipart/form-data" onsubmit="return checkSize(2097152);">

<input id="imagefile" type="file" accept="image/*" name="FileUpload" value="" />