Prefix, showing up where I don't want it to

[Arminios]

I'm trying to set up a prefix system where I have images in their own table instead of the normal prefix text. You can then click on each image, to get threads in similar category.

However, the prefix images show up at least 2 places also where I don't want them, in the navbar and in the "last post" column.

Anyone can help me out with instructions / tips how to remove it in those 2 places?

Look at the first image to see how I want it, and the 2 others where I want it removed.