Why does my iPad send me immediately to the App Store instead of Safari?
Safari was likely last opened to a page that had an iTunes link in it, forwarding you to the App store (similar to ads that people accidentally click on in Games). Try fully closing out the Safari session by double-clicking on the Home button on your iPad, then swipe Safari up from the Multitasker. Then, make sure the session won't reload by going to Settings -> Safari -> Clear website data and history. It will blow your Safari history away but should clear whatever site it has open as well. Note, bookmarks won't be affected by that process :) 

Or try to follow a link from Mail, Twitter etc (whatever opens in Safari), then open the "all tabs" view in Safari and close the 'tab' with the auto-forwarding.