Estate diazo theme has customizable columns width. Default left column width is 185px, while right column width is 200px.
You can change columns width via Site Setup -> Diazo Theme-> Advanced Settings tab.
Note: For Diazo Support extension starting with 1.1b1 version, proceed to Site Setup ->Theming -> Advanced Settings tab.
Specify new values for columnonewidth and columntwowidth parameters in Parameter Expressions textarea. Let's for example set column one width 250px, column two width - 150px.
Now return to the Plone interface and you'll see your changes applied.
