While Spiderman is a Marvel Comics character, Sony Pictures has long held the film rights for the hero, preventing him from appearing in Marvel movies . That’s about to change write Marc Graser and Brent Lang:

• Marvel and Sony have come to an agreement which will allow for Spiderman to show up in Marvel movies.
• This could mean that web slinger may make an appearance in future Avengers installments, as well as cameo appearances in other Marvel movies.
• Sony agreed that it wouldn’t make a dime from Spiderman’s appearances in Marvel films – the publicity and exposure for the character will be payment enough.
• Andrew Garfield will be recast, and a new, younger Spiderman to return the character to his high school roots will be found.

Read details about the agreement here.

Source: Variety