How to customize guestbook entry ?

[dotcom22]

Hello Jan

I would like customize little bit entry...I see I can change background color and other color from admin but I would like make more deeper change like adding a "image line" for separate each entry instead to have a standard rectangle with border...I would like also change font size of title...it is too big for me..I don't find the correct file to edit...

Can you point me to the right direction please ?

thanks