If you are looking for a copy of your return - that is NOT available on any web site. You must submit a request to the IRS to get a copy of your previous return. Here is information on how to do that:
Tax Topics - Topic 156 Copy of Your Tax Return – How to Get One
If you want a true copy of your return it costs $39 and will take 4 weeks or longer. However, you can get a "transcript" of your return for free in about 10 days - the transcript has all the relevant information on it, but is in a much condensed form.