[伪·Ajax]无刷新上传原理

<div id="content">
                <form action="upload.php" method="post" enctype="multipart/form-data" target="upload_target" onsubmit="startUpload();" >
                     <p id="f1_upload_process">Loading...<br/><img src="loader.gif" /><br/></p>
                     <p id="f1_upload_form" align="center"><br/>
                         <label>File: 
                              <input name="myfile" type="file" size="30" />
                         </label>
                         <label>
                             <input type="submit" name="submitBtn" class="sbtn" value="Upload" />
                         </label>
                     </p>
                     <iframe id="upload_target" name="upload_target" src="#" style=";height:0;border:0px solid #fff;"></iframe>
                 </form>
 </div>