Hi Everyone

I am trying to setup my own website, however I am having a bit of trouble my image and the navigation links. My image width and height is set to 400px & 350px I am using the image as a header instead of title name, but when I try to centre the image it takes up half of my website. I have tried using the code. img {display: block; that did put it in the centre but it didn't make the image smaller. I am now trying this code img.display {width:100%; height:auto; but they didn't change anything. Would I need to make the image smaller so that it doesn't take up half of the website.

This might sound like a stupid question but I have always wondered this. When I am coding the links for my menu navigation bar, do I to create a HTML page as well as a CSS page? I always see web pages ending it about.html I'm just are they also using a .css file?

Any help is greatly appreciated thank you.