How to adjust logo size?

The logo size is defined in style.css:

#header .logo{
	float: left;
	width:300px;
}

(Note: the height is proportional to the width)
Change it to fit your needs…

440px is probably the limit if you want to support mobile users

Can anyone breakdown how i can stretch and center my header image. I’m not too familiar with php and the css style sheet