Putting navigation into a <ul> is common practice, but this was before we had the <nav> tag. Back then it made more sense to put navigation into an Unordered List. 

Now that we have the <nav> tag, it is becoming more commonplace to see just a series of <a> tags within a <nav> block. 

There is noting wrong with this approach, but the point is, it is not really necessary to use this approach.