Vendor specific property or at-rule Web Standard


Property or at-rule is vendor specific.


Properties and at-rules prefixed by a dash or underscore, the zoom property and the expression() function are vendor specific and only work on one browser engine.

Applicable standards

  • CSS Validation

Change history

  • 5.29 May 2018 Changed rule ID from W3cCssVendorProperty to W3cCssVendorExtension.
  • 5.4 Feb 2014 Lowered priority to info message.
  • 4.6 Feb 2012 Added.

This page describes a web site issue detected by SortSite Desktop and OnDemand Suite.

Rule ID: W3cCssVendorExtension