CMS event display and data quality monitoring at LHC start-up

The event display and data quality monitoring visualisation systems are especially crucial for commissioning CMS in the imminent CMS physics run at the LHC. They have already proved invaluable for the CMS magnet test and cosmic challenge. We describe how these systems are used to navigate and filter the immense amounts of complex event data from the CMS detector and prepare clear and flexible views of the salient features to the shift crews and offline users. These allow shift staff and experts to navigate from a top-level general view to very specific monitoring elements in real time to help validate data quality and ascertain causes of problems. We describe how events may be accessed in the higher level trigger filter farm, at the CERN Tier-0 centre, and in offsite centres to help ensure good data quality at all points in the data processing workflow. Emphasis has been placed on deployment issues in order to ensure that experts and general users may use the visualization systems at CERN, in remote operations and monitoring centres offsite, and from their own desktops.