what controls issue navigator window width?

Depending on the browser, the issue navigator displays in different widths. Using the exact same login and filter, the column widths vary a great deal because the browser width itself changes from browser to browser. It seems like on Win2000 I.E. I rarely, if ever, get a horizontal scrollbar. On Win XP I.E. and MAC Safari I get a slightly wider window, and on Win XP Firefox, I get a really wide window. I am at home onWin XP so I am attaching those 2 screenshots to illustrate.