(this simulates a 9 second video upload)

A video upload may take several minutes, so a processing message should be used to let the person know it is still working.

Browsers have control once the submit button is pressed, untill all submited data is sent. So we have to use thier abilities. Unfortunately browers do not work the same. Some will not handle the animated gif, and some will not handle the marquee. Here I present both, finding that most/all browsers will support one or the other (maybe both).

I use a div box that is hidden when the page loads. I use onsubmit in the form that calls a javascript to display the hidden div box.
In the hidden div box, is both a marquee "uploading" message, and an animated .gif.

Try it with any browser. Click the submit button ( "Upload" ) button above.