In a single window browser environment, a request to open a new browser window is either allowed or ignored, depending on whether the request was generated in response to user input. The request is ignored if it was not generated in response to user input. If, on the other hand, the request was generated in response to user input, it is allowed. In such cases, in order to preserve the single window interface, the new browser window is opened as a full screen window that overlays the existing browser window. In certain implementations, the determination of whether or not a request was generated in response to user input is simplified by assuming that all requests that are generated during the loading or unloading of a page are not in response to user input and ought to be ignored. By contrast, window open requests that are generated at other times are assumed to be user-initiated and are allowed.