Looking on the internet deeply has found these results:

I have written a letter yesterday. is the most popular phrase on the web.

I written a letter yesterday. 10 results on the web	I have written a letter yesterday. 147 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
It doesn't look like this phrase is very popular! The search could not find any examples on the internet.	Jul 5, 2013 ... I wrote a letter yesterday I have written a letter yesterday. I wrote a letter at 7 o' clock I have written a letter at 7 o'clock. I wrote a letter last�... I have written a letter yesterday. ???? * ??????????????? ??? I wrote a letter yesterday.??????????? Has he gone????????�... I have written a letter yesterday. (wrong!) I have written a letter at 7 o'clock. ( wrong!) I have written a letter last Monday. (wrong!) I have written a�... May 15, 2010 ... (After all, it IS a "present" tense!) I have written a letter yesterday. (X) I have written a letter at 7 o'clock. (X) I have written a letter last Monday. (X)

I written a letter yesterday.

10 results on the web

I have written a letter yesterday.

147 results on the web

More popular!

It doesn't look like this phrase is very popular! The search could not find any examples on the internet.

Jul 5, 2013 ... I wrote a letter yesterday
I have written a letter yesterday. I wrote a letter at 7 o' clock
I have written a letter at 7 o'clock. I wrote a letter last�...
I have written a letter yesterday. ???? * ??????????????? ??? I wrote a letter yesterday.??????????? Has he gone????????�...
I have written a letter yesterday. (wrong!) I have written a letter at 7 o'clock. ( wrong!) I have written a letter last Monday. (wrong!) I have written a�...
May 15, 2010 ... (After all, it IS a "present" tense!) I have written a letter yesterday. (X) I have written a letter at 7 o'clock. (X) I have written a letter last Monday. (X)