After you regenerat, all of the information is replaced. What
I do is copy over all of my customized files (I have them saved to
a "skin docs" directory) to override what is generated.
So first update the whskin_banner.htm file using notepad,
save the file to another directory and copy it to the directory of
your published webhelp. The file will be written over each time you
generate, so you'll have to copy your customized file back in.
Robowizard's skinny on skins is a great tool to lear all of
the customization techniques you'll need and which files you edit.