As a regular internet explorer, I visit a lot of different sites, as a web designer/programmer I am always looking and learning from every half decent site i see.
One thing that I really dont understand, is a holding page that says “Under Construction”. I went to a design site the other day that I have bookmarked. This site, made and maintained by web designers/developers which a good amount of google rank and traffic, have pulled down the complete site, and replaced with;
Under Construction
We are currently redesigning our site, check back on October 25th!
Email: xxxxx@xxxxxx.com
This page for over 2 months will be the front of this design business. Over this time, All of their google rank will expire, all of those inbound links now getting 404 Page not found Errors and any search result will just display:

This to me just doesn’t make sense?
If you have a current site, LEAVE IT ONLINE while you rebuild!
Why lose all your inbound links, While building your site keep in mind the ld sites query string structure! If you are going to alter the linking structure, use Apache Permanent Redirects from the old URL to the new URL!
Building for a New Site
If you are building a site from scratch, you still don’t want bad google indexing. Why not give yourself a head start and create a decent holding page, List as much information as you can! Phone numbers, Addresses, Taglines, email addresses, business/site overview.
This will start giving search engines something to index, and the visitor some information about your site, helping them out, and making them want to visit again.