To manage the displaying messages settings you will need to click on the Settings option in the left hand menu. From there you'll be taken to the Settings page and you can select the Manage Preferences option
If you click on the displaying messages section you'll be given the following options to manage your preferences:
Features
[list]
[*]Open message in a new window: On/off
[*]Show email address with display name: On/off
[*]Display html: On/off
[*]Allow remote resources (images, styles): Never/from know senders/always - display of images linked to in emails (including some formatting controlled by CSS)
[*]Display attached images below the message: On/off
[*]Advanced options: Click arrow to open - allow you to set the default character set
[/list]