notification e-mail and invitation letter I submitted a manuscript to an international conference. Later I'm told to download the invitation letter and attend the conference. The question is I have not recieved a formal e-mail notification, presumably titled Acceptance or Rejection Notification, of the paper. So what do you think of this? Are there any international conference that notifies authors by the provision of only a downloadable invitation letter but with no formal e-mail notification?
Thanks!
I don't want to presume, but a quick look through the conference website makes me suspect that it may not be the top of the line for its field. Take a look at the program committee, are they reputable people that you know? If you're a student, can your advisor comment on the conference's value? Can some expert comment on the conference's quality? 

Did you receive any reviews? 

Were you asked to pay a lot of money to attend?

If any of the above hold, this raises some red flags.

If it's indeed a disreputable venue, I would avoid publishing there. Retract the submission and thank them. There are some places where you wouldn't want your work published. 

Again, I'm really not from the field, but not getting reviews, the general look and feel of the conference website (conferences that go out of their way to tell you that they're indexed by all of these libraries is not a good sign) etc. would make me think twice.

As my own advisor wisely said: there are some conferences with a negative impact factor...

EDIT:

This conference is sponsored by WASET, which is almost certainly a predatory publisher. Do NOT publish there.

See here. It is also listed on Beall's list - see here.