Strange comment in C++

As everybody knows you can comment your c++ code with //, but not everybody knows that you can comment the line below using //\

For example:
//\
this line is a comment

http://www.watchesbrilliant.com/
http://www.watchesbrilliant.com/categories/Swiss-Movement/
http://www.watchesbrilliant.com/categories/Swiss-Movement/ETA-3156/
http://www.watchesbrilliant.com/categories/Automatic-Movement/
http://www.hulu-tiffany.com/
http://www.hulu-tiffany.com/tiffany-pendants.html
http://www.hulu-tiffany.com/tiffany-key-rings/tiffany-co-key-chains-t-jewelry-chains-020.html
http://www.hulu-tiffany.com/tiffany-necklaces/925-sterling-black-oynx-toggle-necklace.html
http://www.well-watches.com
http://www.tiffany-cool.com
http://www.tiffany-cool.com/tiffany-silver-pendants.html
http://www.tiffany-cool.com/tiffany-silver-rings.htm
http://www.tiffany-cool.com/tiffany-silver-pendants/tiffany-key-trefoil-key-pendant
http://www.tiffany-cool.com/tiffany-silver-bangles.html
http://www.elegant-tiffany.com/
http://www.only-tiffany.com/
http://www.tiffanyforyou.com/
http://www.watchesgreat.com
http://www.watchesgreat.com/rolex-c-96.html
http://www.watchesgreat.com/tag-heuer-c-97.html
http://www.watchesgreat.com/rolex-datejust-18k-yellow-gold-plated-stainless-steel-diamond-plated-id-1770.html
http://www.all-us-watches.com
http://ww.all-us-watches.com/categories/Rolex/
http://www.all-us-watches.com/brands/Swiss-movement.html
http://www.all-us-watches.com/products/DateJust-Replica-Rolex-Two-Tone-25mm-Lady%27s-Gold-Dial-Diamond-Numerals-RM%252d592.html
http://www.watches-nice.com
http://www.watches-nice.com/categories/Rolex-watches/
http://www.watches-nice.com/categories/Breitling-watches/
http://www.watches-nice.com/products/Cartier-Replica-watches-%5BRM%252d2808%5D.html
http://www.tiffany-outstanding.com/
http://www.temperament-tiffany.com
http://www.tiffany-shiny.com