When using Drupal your browser returns the following error

The selected file /tmp/file*** could not be uploaded, because the destination ***/***.*** is not properly configured.

This means that the file system path where uploaded files are store during previews is misconfigured. In simple terms Drupal try to upload a temporary file to your server but the process is not working.

An "Internal Server Error" often occurs on:

• Migrating a website to a different server.
• Misconfigured Temporary directory setting under admin/settings/file-system.

To fix this

Navigate to admin/settings/file-system

Under the section Temporary directory: configure the path appropriately. Each server is different. You must type in the appropriate path to your tmp folder on your server. If unsure use a FTP tool. Connect to your server. And search for the folder tmp. If nothing works type in /tmp. This is the most common path.

If above isn't working then using an FTP tool ensure the CHMOD security setting on your tmp folder is appropriate. CHMOD should be 750.