ASP.NET controls opening new windows intead of postback in same window

The fils containing these control work fine in another 开发者_开发百科project and they work fine on visual studio so I guess it is safe to assume that the problem is not in the files or with the server but has something to do with the project? What could be causing this?

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Only a hyperlink with target="_blank" or javascript events will open new windows.

Are you using some javascript enhancement that changes links or adds functionality to them? Could be a lightbox/shadowbox like script.