Padding added in sidebar, not coming from my style sheet [closed]

It sounds like you are seeing a browser default. Most browsers have some styles built in by default which unfortunately often include margins and padding. A lot of developers will put a basic reset on the top of their CSS file, something like

*{margin:0;padding:0;border:none}

This will clear the defaults and only display margins/paddings/borders that you explicitly define.

If you only want to remove the space from that one element, try adding something like this to your stylesheet:

#sidebar{margin:0;padding:0}

This isn’t so much a wordpress thing as it is a general CSS thing to be aware of.