"if you haven't done so yet" "if you haven't already done so"

[herbivorie]

Someone asked me in email to recommend a website where he can review Japanese grammar before he takes a Japanese text.
There is one website I could recommend, but it's kind of popular website, so he may already know it. So can I say:

1. I guess you could try this website if you haven't done so yet.
2. I guess you could try this website if you haven't already done so.

Which is correct? Based on what I learned in school a long time ago, it should be "yet".
But I think I have seen examples like 2 in real life, so I'd like to confirm. Thank you.

 

[bhaisahab]

Someone asked me in email to recommend a website where he can review Japanese grammar before he takes a Japanese text.
There is one website I could recommend, but it's kind of popular website, so he may already know it. So can I say:

1. I guess you could try this website if you haven't done so yet.
2. I guess you could try this website if you haven't already done so.

Which is correct? Based on what I learned in school a long time ago, it should be "yet".
But I think I have seen examples like 2 in real life, so I'd like to confirm. Thank you.

They are both possible. I prefer #2.

 

[herbivorie]

Thank you.
Are there any differences in the meaning between 1 and 2?

Also, how about this?
3. I guess you could try this website if you haven't.