Sidebar right width too small for widgets

Hi there, I experience problems with the sidebar width. Visually there seems to be enough space for a widget, but because of a lack of space the widgets are all shown below the main content in stead of the right side beside it.
I use several widgets, i placed them all in the top sidebar, all other sidebars are empty as instructed. I used the amount of columns = 3 as mentioned in this forum. Still the widgets seem to fit but are all shown below the main content:

my page with too small sidebar

If I just use the layout content/sidebar half, all fits well, but is is not what I want, because the sidebar is 50%. I want it at 33%, so I used the 3 column layout and the top sidebar only as instructed. I also tested with the default layout, so without sidebar. No improvement there.