Trouble changing twentyten sidebar width

I’m driving myself crazy with this. I hope someone can help. So, I’m trying to widen the right sidebar of this site to accomodate the full width of a spotify embed.

Right now the relevent CSS looks like this:

#container {
	margin: 0 -240px 0 0;    

}
#content {
	margin: 0 280px 0 0px;  /*original margin: 0 280px 0 20px; */
}

#primary,
#secondary {
	width: 240px;
}

But I need the sidebar to be at least 250px, not 240px, so that the Spotify embed isn’t cut off on the right side. However, when I change the settings to this:

#container {
	margin: 0 -250px 0 0;    

}
#content {
	margin: 0 290px 0 0px;  /*original margin: 0 280px 0 20px; */
}

#primary,
#secondary {
	width: 250px;
}

…the sidebar content is pushed down to the bottom of the page, to where the main content in the center column ends. What am I doing wrong?

Thanks ahead of time.