Apply to all mediums: With this checked, everything in this section will apply to all of your connections.
Show Text Formatting: Check this if you want to see your buddies font and color changes.
Show Emoticons: Shows emotes like smiley faces if your buddy types them in. If unchecked you will see the characters :)
Play Emotisounds: Plays the sounds attached to an emote if there is one included.
Show Time Stamps Shows timestamps in the chat window as well as the log
Format: Choose how you want the timestamps to be displayed.
Miscellaneous
Autofit images into display: Changes the size of images to fit in the window.
Links activate on double click: Double clicking a link in a chat window will take you to that window. Left unchecked, single clicking performs the action.
Links open in a new browser: Links will open a new browser when clicked. If unchecked the link will activate in your current browser.
Text buffer (in lines): The amount of text to show within the display area of the chat window (if you have "Auto show history within new message windows" checked in the Preferences->Message History section
Scale Emoticons to size: Makes the emotes the same size as your font.
Show last focus line marker: When chatting with a buddy and you change focus, Trillian will put a line in the conversation to show where you left off (your window only)
4. 
4.1. 
