Censuses were taken in Scotland every 10 years from 1801, but they became more detailed from 1841. They have been indexed from 1841 to 1911 on scotlandspeople.gov.ukk (later censuses are closed for 100 years). Some pre-1841 censuses have survived.
Only the enumerators’ returns survive for 1911, not the original householders’ forms. ScotlandsPeople is the only website that has the original images for 18411911. However, better use of pay-per-view credits can be made by searching the free 1841-1891 indexes on familysearch.org.uk. The full range of indexes for 1841-1911 are available at ancestry.co.uk and findmypast.co.uk, and thegenealogist.co.uk has a sample of the 1851 Scottish census.