Any “Watch This Space” or “Under Construction” placeholders you see on sites mean little to the typical visitor. Their interests coincide less with your corporate interests than you could ever imagine.
Evidence: Bounce rates on sites of 50% or higher are the norm. A typical adult web visitor has little patience for the sort of peekaboo he or she enjoyed as an infant.
Worse than irrelevant, posting these types of notices for long periods of time place you at risk of being demoted by search engines and disregarded forever by the users would were turned away.
Take aways: Post these types of notices only as necessary. Should you need to, post them only very briefly. Consider following these “reconstructions” with a strong promotional push, to help woo visitors back to your site and your brand.