adverts in header

[peterpigman]

I am trying to place an ad in my header but due to being a noob. I am having problems. I am looking to place a button ad here...

Attachment 75571


But I am obviously doing something wrong as whichever way I do it it either ends up above, below or knocking the main header off centre. Anyone point me in the right direction? I did a search but couldn't find any answers.