This post is also available in: 日本語 (Japanese)
It is the introduction when you scroll the page, the sidebar comes with an automatic(sticky sidebar) plugin "Q2W3 Fixed Widget(Sticky Widget)".
By the way, please note that will stop the adsense account if use a sticky sidebar to the google adsense.
Q2W3 Fixed Widget: How to setting
Setting in the "Appearance > Fixed Widget Options".
There is no problem if you set only the contents of the "General Options" below.
Margin Top:Space setting of the upper part of the widget
Margin Bottom:Space setting of the lower part of the widget
Screen Max Width:Plugin will be disabled when browser window width equals or less then specified value
Please try to put a check the "Use jQuery(window).load() hook:" of Compatibility,if a problem occurs with the plug-in system scroll other.
Using Q2W3 Fixed Widget
In the pages of the "appearance> widget", check box labeled "Fixed widget" has been added to the widget, put a check to the widget you want to Sticky Widget.