fixed typo on page 3
fixed typo on page 11
Update lecture4.html

fixed typo on page 20
fixed typo on page 26
fixed typo on page 36
fixed typo on page 7
fixed typo on page 7
fixed typo on page 8
fixed typos on page 14
fixed typo on page 18
fixed typo on page 18
fixed typos
Merge remote-tracking branch 'remotes/origin/patch-1'
Merge pull request #1 from prasopes/master

Fixed some typos in the slides.