Bar at the top auto resizing itself with logo image

Hi there,

When inserting our company logo at the top of our website the white background to the top dropdown bar resizes itself and leaves a huge gap beneath everything.

Link to my website: http://www.destiny-game.info/carrentals/

As you can see where our logo is at the top right it fits nicely however the white background to it, and the dropdown bar with “About, Home” etc has resized itself along with the image, i would like the image to overlay this and stop it from resizing.

Sorry if I’ve explained this badly, any help is appreciated.