HTML list <ul> not showing items <li> on a new line

I created a standard HTML list to show all items on a new line. For some reason, when the text related to one item is short, another item is displayed on the same line (not below it). Do you have any idea how to add some line break into the list, to display items vertically ?

Hi,

To display the list items vertically, try to add clear: both; in CSS for <li>.