Our website has a global horizontal main menu that drops down to show all second-level navigation items.
We have requirements to build our website no wider than 1000px (according to web stats of visitor resolutions). We also have advertising requirements that force us to have a right hand column on every page.
I tried inserting a left hand vertical navigation to show all second-level navigation items, but this means that our main content column (between the left and right and columns) is too narrow for the graphs and tables (up to 11 columns) required on most of our products and services pages. The only option I saw was to remove the left hand column navigation to retrieve some of this space. The results are that I then had ample room for our graphs and tables.
What this means though, is that if a visitor is on a second-level or third-level page, the only way for them to access other second-level pages is by clicking on the main menu again and selecting a menu item.
What is the standard on always showing/not-showing second level navigation?
My concern is that for all of our non-products and services pages, a left hand vertical navigation may be ok because we don't need all of the horizontal space for tables and graphs.