Position-in-Middle.js

//It will work for the element that has position: relative

function postionMiddle(e) {
	var	capHeightHalf = $(e).innerHeight() / 2,
		capParentHeightHalf = $(e).parent().innerHeight() / 2,
		capPosition = capParentHeightHalf - capHeightHalf;
	$(e).css("top", capPosition );
	}	
	postionMiddle(".caption"); // place your element instead .caption




//If you want to pass multiple value inside the function or want to plus/minus from the output value
/*	function postionMiddle(e, v) {
	var	capHeightHalf = $(e).innerHeight() / 2,
		capParentHeightHalf = $(e).parent().innerHeight() / 2,
		capPosition = capParentHeightHalf - capHeightHalf;
		
		if (v == null){
			$(e).css("top", capPosition );
		}else{
			var capPosition2 = capPosition - v;
			$(e).css("top", capPosition2 );
		}
	}

	postionMiddle(".caption");
	postionMiddle("nav", 32);
*/