Website Layout

I am very inexperienced right now in creating web sites, but my church
has asked me to create one for them. I was wondering how you guys
take into account the way that your site looks on each user's machine
with regards to the user's monitor size and resolution? I have found
that you are able to set the height or width of an object to a
percentage of what I am guessing is the height or width of the page,
but my problem with that is that I have a flash video playing at the
top. Originally I had set the height and width of all my objects
using pixels. So I created the width of the video to be the same
width as a panel right below it. But, if I make the panel a relative
percentage of the page, then the video would not line up with it since
the video will have to be a set size. Do you guys use the pixels or
the percentage of the page when setting the height and width of an

Thanks for any replies.