I have a cloud mask shapefile that accidentally identified buildings as clouds. I want to delete this mass of polygons in Arcmap 10.1 by highlighting all of them and pressing delete. Then re-saving the shapefile. Right now I can only highlight one at a time through clicking and pressing delete. It is taking a long time. Is there some settings I need to change?
Try changing the selection mode in ArcMap to
Add To Current Selection. Then you can select multiple features. See the link here for a discussion:
To select multiple features in ArcGIS 10.1 you can open up the feature layer's attributes and choose select by attribute. This will allow you to filter the selection by using certain fields to mark the features to be deleted. Along with that you can invert selection if you are able to easily select all of the features that you want to keep and then switch it to the ones that you want to delete. Both of those buttons can be found at the top of the Attribute Table window.