Hi Mike, Since i ve changed homepage as default one i didnt get that problem(underconstruction.html). So the problem is gone... I am suprised that i have this kind of problem.. it was really annoying .. Thanks your timing and thanks ....

If it's intermittent you can change it when it does load for you. Or you can go into the db and change it directly in the table. I'm not sure of the actual table/field, but DNN does a decent job of using logical names. Poke around in the tables and i"m sure you'll find the one in question where you can update the home page. Also, you can check your windows event viewer. It could shed some light on the reason for the error.

I hope this helps some who are experiencing the same problem.  About two weeks ago, I switched from SQL Express to SQL Server.  Since then, this error ("This site is currently unavailable.  Please check back later.") has not recurred.  Furthermore, the site loads much faster.  For what it's worth, SQL Express seems to have been the weak link.