Added text from item #1 of HW4 part1-instruction
Added text from item #2 of HW4 part1-instruction
Added text from item #3 of HW4 part1-instruction
Added text from item #4 of HW4 part1-instruction
Added text from items #5,6 and 7 of HW4 part1-instruction
Added text from items #8 and 9 of HW4 part1-instruction. Deleted unnecessary lines
Fixed some syntax errors in various URLs
Fixed some syntax errors after validate by W3C
Fixed some syntax errors