We are all very familiar with the White Screen of Death in the Drupal world, AKA WSOD. One very common cause is a lack of memory for PHP - yet another is having errors turned off.

In development mode, you should probably make sure you are showing PHP errors on the screen, if this is an option. This is the kind of thing you can edit in your site-specific settings.php file, by using:

A common development practice is to keep a local web server running on your laptop, or a development/staging server. A feature of Drupal designed for multisite installations can actually help you out in this situation.

Different servers often mean different databases, database users, and passwords. Sometimes, you may also need to point to a different files/ directory or tmp/ directory, especially if you are moving between Windows to Linux, or a local machine to a server.