Drop down menu visibility

I am in the process of building a drop down menu. I have the menu in a 2 row 1 column table. In the first row is the menu, the second contains a signup bar. When I scroll over the menu, the dropdowns go behind the bar/other row in the table. I tried using the overflow command, but it doesn't seem to be working. How can I get the menu to stay visible above the row/bar?