I'm looking in HTML, and am making a button. How can I change the border thickness?

Thanks

Edit: I've found the solid part, but what are the other options?

I've got a link here so I can ask several more things.
http://www.wn.com.au/hearingsw/moylance/test.htm

See the button, how can I make it affected by the links props from the CSS? I want it to have hover, and other stuff.

I want the border smaller, as that looks a little dumb. I've learnt so much and things have caught on.

The page cannot be found....

Have you checked out Lissa's CSS section?
http://www.lissaexplains.com/css.shtml