var m_left_height = document.getElementById("m_left").offsetHeight;
		var m_right_height = document.getElementById("m_right").offsetHeight;
		var m_interval = m_right_height - m_left_height;
		if(m_interval > 20){
			document.getElementById("s_back_image").style.height = m_interval - 20 + "px";
			document.getElementById("s_back_image").style.display = "block";
		}