Re: CSS Tweaking in BP Member Theme
For custom CSS, it’s best to create a file called “custom.css” in your theme — see the “custom-sample.css” in the theme (you can copy that file, rename it to “custom.css”, and modify it).
For the border, you can probably use the #main element, like:
border: 1px solid red;
The reason the border doesn’t go all the way to the bottom of the element in your current setup is that there are floated elements inside of it — meaning that the parent element does not wrap them. Using “overflow:hidden” is a nice way to wrap those floats.