This prophecy, just like Genesis 12:3, is an ongoing perpetual prophecy that was declared in the time of Joshua, and still remains in effect today, and will continue to do so until the end of the Millennial kingdom.  Here's the basic premise of the prophecy:

“Cursed be the man before the Lord who rises up and builds this city Jericho; he shall lay its foundation with his firstborn, and with his youngest he shall set up its gates.”

In other words, anyone who builds in or around the ancient city of Jericho will suffer severe loss and devastation among their family.  This can also apply to a nation if they are acting corporately rather than individually.  We see this prophecy being fulfilled in modern times in the way that Israel is being cursed for their participation in building projects in Jericho.