[Theme:Holi] Left justify header

Hi all.

Currently my header image is centred at the top of the page. I would like it to be left justified.
My header has a logo on the left hand side and I would like it to be at the top left of the page no matter what size the window is.
Currently as the page is made smaller it cuts the left and right of the image off.
I have the “custome css manager” installed, so can add css there if required.
I have tried an few bits of css but have not managed to fix the problem.
Aany pointers welcome.

Thanks.