if you already have codes that are supposed to edit the header for you, but they're not showing up correctly, it may be because you don't have a website defined in your profile.
the codes to hide your journal's default header and replace it with one of your own are as follows
in your GLOBAL_HEAD tag, under the <style> tag, paste this:
then enter this AFTER your GLOBAL_HEAD tag
make sure the coding in between the LASTN_WEBSITE, FRIENDS_WEBSITE, and CALENDAR_WEBSITE tags are all identical. you can edit the font, size and colour to whatever you want.
FULL DISCLOSURE: this is not my coding. i don't think it's from ~coding (the layout it's from isn't credited to them) either, idk.