typo
fixed wrong link to appmanifest validator
changed link's name
minor enchancements
changed item's name in details list, fixed link to point to correct line
redirected links to the correct line
fixed introduction to Web API and WebActivity
'Visualizzazione flessibile' is now bold everywhere and a hint to acces the new developers tools has been added
added http section
editing and review
merging from @Mte90