I am building a calendar web page using jQuery and asp.net-mvc similar to this and I can’t figure out how this example is supporting events that span multiple days (it shows the event as a single item across multiple days in the view).
Using firebug, I see that the calendar is simply a table:

but I can’t figure out how they have the event div that crosses multiple cells of a table like the “Long Event” in the image below?

Combining the answers above:
you may need to provide a z-index to ensure that your element appears on top of other table cell contents..