Spider-Man picture with my caption
One thing I’ve noticed is that until the 1990′s Spider-Man had a great, almost easy to follow continuity. His history was not really messed up, or had big gaps of reboots, timeline jumps, or continuity problems.
I’ll qualify this by giving bad continuity examples. Over at DC Comics, Superman, Batman and everyone there no longer follows their history from the Golden Age. In the 1980′s the Crisis event was a company wide reboot that redid everyone’s origin. Then in the 1990′s they had things like Zero Hour, which were again reality shaping events.
The Marvel heroes had much less continuity trouble. Though their was trouble with other Marvel characters, such as Iron Man who was clearly dead. Replaced with an alternate timeline teenager. A great example of a continuity and story mess.
But Spider-Man history did not have much trouble at all. His history from the 60′s could fit and explain a story in the 1980′s.
Then what I consider the first big Spider-Man history changing event happened. And that was the 1990′s Clone Saga. With this event, vast Spider-Man story ideas and history was rewritten and changed. Characters like Ben Reilly being on the road alive. Kaine a killer clone out there. The first Clone Saga Jackal story and what we saw was greatly changed. This result had Peter made to be the actual clone.
And after this history rewrite event, to get out of the mess they had to rewrite the history they just made.
This process and clone saga end brought back Norman Osborn, who got all the blame for the event. And a character who in my opinion meant more to the Spider-Man mythos dead than alive.
The next timeline changing event was the John Byrne Chapter One Spider-Man reboot. With the long standing Spider-Man issue numbers having a reboot back to issue one. This redid Spider-Man history, and it sort of just disappeared with no clear understanding how it was phased out.
This mysterious fade out also happened a few years ago with Spider-Man The Other. With no questions of how is it possible and did Peter really shed his skin? What happened to his wrist spikes? And how convenient after all these years he now gets movie style organic webbing, only to have it eventually disappear.
As well as J. Michael Straczynski’s “Sins Past” story. It was more of a sin to defile innocent Gwen Stacy. His story reduced Gwen into a stereotype, nothing but an easy to influence, weak willed blond and a whore to boot.
But perhaps the most recent and biggest history event was the One More Day mess which redid history. Got rid of the marriage and mind wiped the public of them knowing Peter’s identity. The blame for all this goes to the demon Joe Quasada, oops I meant to say Mephisto. Yes, that is who is at fault. 
But this being comic books and all, I think the Spider marriage, what I’ll refer to as the “original timeline” Spider-Man that many grew up with is still around.
What we have now since One More Day is a Spider-Man and history from an alternate timeline. His history and what we are reading now branched off when Mephisto went back to the past and got rid of the marriage.
This does not mean that the “original timeline” Spider-Man does not exist. It merely means we are no longer reading his published adventures. We are reading the adventures of an alternate timeline Spider-Man.
It’s the whole paradox of a time travel. Such as a time traveler going back to the past to undo the event that lead him to make a time machine. How could he go back to the past and correct it? Because without that past event he would not exist as he is today.
The same with the Spider marriage, if it never existed. How could Mephisto go back and change it? It had to have existed in the first place.
And wasn’t it established in Marvel, and in possible real life theory. That if time travel does happen, what the traveler is doing is actually creating or jumping into new alternate timeline realities. He did not effect or change his timeline reality. Rather he created and jumped to a new reality. And that the whole concept of multiple realities is in fact what really happened.
And I think it’s been mentioned in a story that when Kang the Conqueror jumps in time, he’s actually creating or jumping into different realities.
As I mentioned at the start, up until the 1990′s Spider-Man had a clear history, and probably one of the best of any superhero long running series. About 40 years of easy to follow history.
Then the various rewrites, reboots and other such reality shaking events happened in the book. It’s now at a point I think of pick and choose your Spider-Man history. And if the recent few years is an indication, I would not be surprised if another reality shaking event in Spider history happens in a few years.