Here are some other considerations.

Some Browsers may require additional header information.
The assignment may tell you to assign some values before the rest of your program
You might want to simplify your life by defining the function pr()
Your Homework will need to identify who you are.
You might want to add some aesthetics

<html><body><script type="text/javascript">
width=3; llength=5

function pr(x){document.write(x,"<br>")}
pr("Engr 190 Assignment #0 by My Name")
pr("<big><center>Hello world!</center></big>")
pr("<p>The length is: "+llength)
pr("The width is: "+width)
area=llength*width
pr("<b>The area is: "+area+"</b></p>")
</script></body></html>

and that will generate this output if you open it in a browser:

Still More JS