Our website is organized with three panes: a banner at the opt (toppage.html), and index column on the left side (sidepage.html) and variable pane on the right. The content of this pane is specified by link in the index column or in a URL intended to go directly to a specific page.
That general address is supposed to open the three-pane opening page.
For the past few days the general address has linked directly to one of the variable pages or to "This page uses frames, but your browser doesn't support them". But it doesn't open the three-pane opening page.
This happens inconsistently depending on the computer being used.