I have decided that I’ll probably use godaddy to host my all-Flash website.
But before I begin to create the site in Flash, I need to know how large the screen size should be.
What is the average Flash website size?
How many pixels by how many pixels should my website be?
Is there a limit to how big of a length-by-height GoDaddy will accept?
Thank you so much for any knowledge or advice you can impart. 
You can design the flash site to adjust to any viewers browser screen. Generally you should be designing to fix 1024 x 768 resolution. That is the minimum monitor size today. No one really uses 800 x 600 anymore.