You can view and set the media player's volume from your iPhone or iPod touch.
You can also directly set the volume to a specific level by tapping on a position within the volume bar. The volume will be set to the point at which you tapped. This volume bar will also update to show the current volume level if it is changed from within your media player.
Note: Sliding your finger across the volume bar cannot be used to adjust the volume, as Safari reserves the slide gesture exclusively for scrolling.