Ideally, it should set itself to the width of the widest item that will appear in the second column.
To make it work like this, I replaced "display: none" with "visibility: hidden; height: 0px;", and I replaced "display: inherit" with "visibility: visible; height: auto;". So, while the viewport width remains the same, it will no longer jump between a one column display and a two-column display. At the viewport width where it would have been doing this, you will now just get a one column display.
To make it work like this, I replaced "display: none" with "visibility: hidden; height: 0px;", and I replaced "display: inherit" with "visibility: visible; height: auto;". So, while the viewport width remains the same, it will no longer jump between a one column display and a two-column display. At the viewport width where it would have been doing this, you will now just get a one column display.