Multiple Browser Tabs/windows Sharing Data?

I have a page where I display ASP.NET charts. There are two types of charts and I felt the need to separate them to some extent which I did by using a submenu which looks like this:

Charts > Goals Charts
> Reconciliation Charts

Clicking on either of the two chart links will take you to the same Charts.aspx page, but with the query string "Goals" or "Reconciliation" respectively. On the page load of the Charts.aspx page, I receive the query string into a session variable and create the correct charts based on that value. All of this works fine.

The problem I'm experiencing occurs when I open up a new tab in IE/Firefox. Here is the series of events I'm experiencing:

- In the original tab, I will click on the "Goals Charts" hyperlink which loads the Charts.aspx page with "Goals" as the charts type session value. The other controls on the page needed to produce "Goals" charts (eg. drop down lists, etc) are displayed correctly ie. the "Goals" version. At this point, I haven't done anything in this tab except for loading the Charts.aspx page from the "Goals Charts" link.

- In the original tab, I right click the "Reconciliation Charts" link and opt to open in a new tab (I just tested and the same thing appears to be working if you opt to open in a new window as well). When the new tab loads the Charts.aspx page, it loads with the query string "Reconciliation" which it stores in the session variable. So at this point I would expect to have two different, independent tabs: the original tab on the "Goals Charts" track and the second tab on the "Reconciliation Charts" track.

- This is where the problem occurs. I would expect the original tab/window to create a "Goals" chart when I make a selection using the other controls and I would expect the second tab/window to create a "Reconciliation" chart. The problem, however, is that when I go back to the original tab/window - the one which should be a "Goals" chart and which should have "Goals" stored in the session value - when I proceed to create a chart, it's a Reconciliation chart that is created.

Somehow, even though I'm in a different tab or window and I am navigating the site seemingly independently of the other tab/window, it seems to be carrying the most recently populated value from the session variable for both tabs/windows.