I do not wish to cause undue alarm or panic but I would like to suggest that, for now, visitor stay away from the Taksim area.
There is an ongoing peaceful protest against the destruction of Gezi park to make way for a new shopping mall (which of course Istanbul desperatley needs!) that the police have repeatedly attempted to break up using what amnesty international have described as excessive force. This force includes the use of tear gas and water canons. News sources are reporting 'According to the Istanbul Chamber of Medicine, seven people have been seriously injured. Six people are suffering from serious head trauma, while a teacher’s leg has been broken.' Alternative news source report at least one person has died. These source and images from social media are reporting that the Taksim metro station has been locked down and tear gas fired into the station whilst people are trapped inside.
At time of writing this is an ongoing situation.
DHA have been giving a live news feed but I don't know how long this will be allowed to continue.
These are in turkish but some unfortunately graphic images
To those regulars to this forum who will no doubt want to down play this and have this thread removed please do not, even you cannot seriously want to endanger the welfare of visitors by pretending this isn't happening.