The bubble around the buttons and the tab borders around the buttons on the tab bar.
To change it You basically have to jump in the skin.ini that you can find in the zip of the skin.
To remove the borders on the left of the pagebar(or tab bar) you'll have to remove the stuff beginning with [Pagebar Tail and [Pagebar thumbnail tail
Now let's go to the left where the panel toggle is
You'll need to remove [Pagebar Head... and [Pagebar Thumbnail Head...
This is what you get.
For the bubbles on the address bar you hve to remove the "Address bar Button Skin" section
In any case remember that you've got also left, right and bottom.
This will result in the following
NOTE: that if you remove to much, that the bubble around the buttons also disappears when you're mouse is hovering above.
In the native skin there seems to be a bug hat the Closed tabs button on the right on the page bar sits on an tab.
This can also be fixed in the skin.ini in the windows.zip pakkage.
Now you'll have to ad something and not remove
[Pagebar Tail Button Skin]
native = 1
This should do the trick.
Have a nice day