Fixit – CSS Expression

This test determines if your page makes use of the CSS expression directive. The expession directive encapsulates Javascript code into CSS rules, effectively mixing styling data with functional logic. This is considered bad practice as they will affect page load time. But these Javascript expressions will also be re-evaluated when the user scrolls or interacts with the page.

Checking for CSS expression

This test checks to see if the tested page makes use of CSS expression directives. If the expression directive is detected in the page CSS then the test reports a FAIL.

If you receive a FAIL for this test, you should consider removing the CSS expression directives.

Reference

This test is based on a YSlow best practice. See http://yslow.org/faq/ for more details.