Hi,
I suggest this.
Put your address in the top right corner, followed by the date.
Below that, and on the left, put the name and address of the person you are writing to.
Dear Mrs. Smith,
Please note that I started my job in website development with this company on July 2nd, 2007.
Yours sincerely,
sign your name
Then print your name.
If people are very, very polite in your country, you might want to add some more polite words.
Best wishes, Clive