when the drop-down button is clicked, the page will follow 
the middle code of the drop-down box is:
padding: 10px 0;
overflow-y: auto;
max-height: 413px;
when the drop-down button is clicked, the page will follow
the middle code of the drop-down box is:
padding: 10px 0;
overflow-y: auto;
max-height: 413px;
the drop-down box should be absolutely positioned to the appropriate position. Visually, you are not absolutely positioned