"If I saw you yesterday I would say hello" is not correct. "If I saw you" is not possible as a counterfactual: you must say "If I had seen you". "If I saw you" may be possible in non-counterfactual situations, e.g. "If I saw you yesterday I don't remember it".

The word "I" should be capitalised. "i" is always incorrect.

Sentences should begin with a capital letter.

Thanks a lot for response but xan you tell me why do we say : Sorry if i OFFENDED you isn't past meant saying this or is it considered as unreal situation e.g : If i HAD money, I would buy a house ?

"I am sorry if I offended you". The speaker admits the possibility of offending the other person in the past,

"If I had money, I would buy a house." The speaker is speaking of the present/future unreality of having money.

Thanks a million.. You helped me a lot. I'm trying to match the conditionals with my language.In my language we use just If+past simple to mean past. e.g : If I invited Jack yesterday he would be happy..According to your answer sometimes it has the same meaning in english as well.. But it's not shown in grammar book (Raymond Merphi,Martin Hewing) I would be grateful if you give me source where i