Older Windows wants 3 letters. If you omit one the page may not work. Almost all the tags need closure and ALL file requests need quotations around them. Keep the size of pictures small. Most all things you download from the Web will already be compress to a small size.
Large files load very slowly.
For the sake of a number, keep pictures under 100k in max. You ll see that most small clipart, etc. is actually less than 10k. We expect you to work on your page until the beginning of May and then move it to a server. On May 4th we would like everyone to have something on a server and the address to that site in our hands. In that way we can look at the material, you can make changes if necessary, and get the site updated by the end of the semester.