Changing css id & classes

Please can someone tell me if there is a way to change how my ID and classes are written in the styles.css? At the moment BS is writing them as div#header.col-lg-12.col-md-12.col-sm-12.col-xs-12. I just want it to read #header.. Is this possible?

simply click in the stylesheet on "#header.col-lg-12.col-md-12.col-sm-12.col-xs-12." and delete everything till "#header"

Yeah just discovered this myself. Thanks