This tab is based off of this cover http://www.youtube.com/watch?v=CVdEEx_tsT4.
Follow it for guidance.
Ah-ah...Ah-ah... (clean) X5
D|-----------|
A|-----------|
D|-----------|
G|-------8-7-|
B| 8---------|
E|--8--------|
(clean)
D|------------5-| X3 End with this
A|3---6---5---5-| A|-3
D|5---8---7---5-| D|-5
G|5---8---7-----| G|-5
B|--------------|
E|--------------|
(overdrive)
D|---------------------------5-5-5-5| X1
A|3-3-3-3--6-6-6-6--5-5-5-5--5-5-5-5|
D|5-5-5-5--8-8-8-8--7-7-7-7--5-5-5-5|
G|5-5-5-5--8-8-8-8--7-7-7-7---------|
B|----------------------------------|
E|----------------------------------|
. . . . . . . . . . . . . . .
D|---------------------------5-5-5-5| X2 End with this
A|3-3-3-3--6-6-6-6--5-5-5-5--5-5-5-5| A|3-3-3-3-3-3-3-3-3
D|5-5-5-5--8-8-8-8--7-7-7-7--5-5-5-5| D|5-5-5-5-5-5-5-5-5
G|5-5-5-5--8-8-8-8--7-7-7-7---------| G|5-5-5-5-5-5-5-5-5
B|----------------------------------|
E|----------------------------------|
. . . . . . . . . . . . . . . .
Chorus
D|------------------6-6-6-6--3-3-3-3| X3 End with this
A|3-3-3-3--6-6-6-6--6-6-6-6--3-3-3-3| A|3--
D|5-5-5-5--8-8-8-8--6-6-6-6--3-3-3-3| D|5--
G|5-5-5-5--8-8-8-8------------------| G|5--
B|----------------------------------|
E|----------------------------------|
Ah-ah...Ah-ah... (clean)
D|-----------| X2
A|-----------|
D|-----------|
G|-------8-7-|
B| 8---------|
E|--8--------|
(overdrive)
D|---------------------------5-5-5-5| X1
A|3-3-3-3--6-6-6-6--5-5-5-5--5-5-5-5|
D|5-5-5-5--8-8-8-8--7-7-7-7--5-5-5-5|
G|5-5-5-5--8-8-8-8--7-7-7-7---------|
B|----------------------------------|
E|----------------------------------|
. . . . . . . . . . . . . . .
[ Tab from: https://www.guitartabs.cc/tabs/a/avril_lavigne/forgotten_tab_ver_4.html ]
D|---------------------------5-5-5-5| X2 End with this
A|3-3-3-3--6-6-6-6--5-5-5-5--5-5-5-5| A|3-3-3-3-3-3-3-3-3
D|5-5-5-5--8-8-8-8--7-7-7-7--5-5-5-5| D|5-5-5-5-5-5-5-5-5
G|5-5-5-5--8-8-8-8--7-7-7-7---------| G|5-5-5-5-5-5-5-5-5
B|----------------------------------|
E|----------------------------------|
. . . . . . . . . . . . . . . .
Chorus
D|------------------6-6-6-6--3-3-3-3| X3 End with this
A|3-3-3-3--6-6-6-6--6-6-6-6--3-3-3-3| A|3--
D|5-5-5-5--8-8-8-8--6-6-6-6--3-3-3-3| D|5--
G|5-5-5-5--8-8-8-8------------------| G|5--
B|----------------------------------|
E|----------------------------------|
Interlude - the 0s are actually 10s.
D|------------------------------------------------------------------| X3
A|3-3-3-3-3-3-3-3--6-6-6-6-6-6-6-6--5-5-5-5-5-5-5-5--8-8-8-8-8-8-8-8|
D|x-x-x-x-x-x-x-x--x-x-x-x-x-x-x-x--x-x-x-x-x-x-x-x--x-x-x-x-x-x-x-x|
G|5-5-5-5-5-5-5-5--8-8-8-8-8-8-8-8--7-7-7-7-7-7-7-7--0-0-0-0-0-0-0-0|
B|------------------------------------------------------------------|
E|------------------------------------------------------------------|
D|-----------------------------------------------------------------| X1
A|3-3-3-3-3-3-3-3--6-6-6-6-6-6-6-6-6-6-6-6-6-6-6-6--8-8-8-8-8-8-8-8|
D|x-x-x-x-x-x-x-x--x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x--x-x-x-x-x-x-x-x|
G|5-5-5-5-5-5-5-5--8-8-8-8-8-8-8-8-8-8-8-8-8-8-8-8--0-0-0-0-0-0-0-0|
B|-----------------------------------------------------------------|
E|-----------------------------------------------------------------|
Chorus
D|------------------6-6-6-6--3-3-3-3| Repeat until end of song
A|3-3-3-3--6-6-6-6--6-6-6-6--3-3-3-3|
D|5-5-5-5--8-8-8-8--6-6-6-6--3-3-3-3|
G|5-5-5-5--8-8-8-8------------------|
B|----------------------------------|
E|----------------------------------|