It has been correctly pointed out that the syllabus is not very explicit about the contribution of Web-HW to the grade.  T have made the following decision which slightly modifies what is said in the syllabus:
Lab 20%
Recitation 10%
Web Homework  6%
Lecture quizzes  4%
Midterm 1 14%
Midterm 2 14%
Final Exam 32%
total 100%

Advice on Web HW.
Although I definitely want you to do the web homeworks, I do not necessarily want you to get perfect scores.  Sometimes you may learn more by not trying to finish the problem.  If you have thought hard and are getting frustrated because the computer isn't accepting your answers, I recommend not getting more frustrated.  The ideal thing is to read the relevant part of the text over again, look for a similar example problem, etc., and try again next day.  A less ideal solution, which you should be willing to use occasionally, is press the button "show me the answer."  You will be given a 0 for that part of the HW, but you will have now a chance to think about the actual answer and why it is different from the one you were trying to enter.  One thing I am implicity saying is that a perfect web HW score is not necessarily the best way to get an A in the course, if it involves unnecessary extra frustration.  High scores on the exams is the best way to get an A.  For this to happen you have to learn the material.  The web HW is supposed to help.  But getting frustrated with web HW is obviously no help.

The first 3 lecture quizzes show about 2/3 right answers.  But you can get 1/3 by blind guessing.  I recommend strongly that you think about the problems that you didn't get right on these quizzes.  The correct answers are all posted on the web.