As Hc4361 suggests, if your task bar is simply in the wrong place, 'click-&-drag' to get it to where it should be. (Then right-click on it and select 'Lock Taskbar' to stop it moving again).
If it seems to have disappeared altogether, try moving your cursor right to the bottom of your screen. If it then changes to a double-ended arrow it's resting on the top edge of the task bar. Click & drag to pull it up a bit.