As title is very clear what this post is about I will not write long description. I have listed definition of FILLFACTOR from BOL here.
FILLFACTOR
Specifies a percentage that indicates how full the Database Engine should make the leaf level of each index page during index creation or alteration. fillfactor must be an integer value from 1 to 100. The default is 0.
T-SQL Script to set Server level FILLFACTOR to 90
EXEC sys.sp_configure 'show advanced options', '1'
RECONFIGURE WITH OVERRIDE
GO
EXEC sys.sp_configure 'fill factor (%)', '90'
GO
RECONFIGURE WITH OVERRIDE
GO
EXEC sys.sp_configure 'show advanced options', '0'
RECONFIGURE WITH OVERRIDE
GO
Reference : Pinal Dave (http://www.SQLAuthority.com), BOL
pinaldave
