I heard recently that both the sender & recipient addresses are suppose to be on the left side of an application letter. what baffles me is that most people condemn me when I write an application letter in that format. Now, my questions are as follow
1) is it really proper to write both addresses on the left side?
2) is it proper for the name & signature at the bottom line to be place on the left side?
thanks in advance...

As for the closing remark, it is good on the left side. The address of the sender should be at the right side. You can also use letter head - writing your name, address, phone number and mail at the top or the letter. That is basically called a Cover Letter. It is the same thing as Application Letter so don't be confused.