On the death of William the Conqueror, he had divided his lands between his two eldest surviving sons, making Robert Duke of Normandy, while William II became King of England. However, Norman nobles (who now held land in both England and Normandy) felt that Robert would be the preferable king, since they saw him as weaker and easier to disobey. In 1088, therefore, they rose in rebellion in favour of Robert taking the throne, but Robert himself never arrived on the scene to support them, so the rebellion was a failure.
Editors. "Rebels support Robert Curthose". The Literary Encyclopedia. First published 31 July 2012
[http://www.litencyc.com/php/stopics.php?rec=true&UID=1951, accessed 19 September 2014.]