Why use a dead link?
Dead links can be used as an alternative to linking to the home page. The default behaviour is for links to appear active on their specified page, if all your links are pointing to the home page, on the home page they will all appear active like this:
As opposed to this:
To make a menu link unclickable, i.e. a "dead link", you can head into Online Store > Navigation. In your Main Menu choose the link you would like to make into a dead link. Click "Edit", in the "Link" field add "#" So it looks something like this:
This will not effect any dropdown menus attached to these links, they will function as expected :)