Cascading style sheets (CSS) is a Web-based style sheet language that is used for the presentation of Web documents. CSS has advanced from CSS1 to CSS3.and extensions to CSS known as CSS pre-processors have also emerged in the last few years. As is the case with regular software, CSS have inherent complexity that keeps on increasing with age which is undesirable, and metrics are needed to measure with the aim of controlling it. Although several Web metrics have been proposed in the literature, the area of stylesheets is still lagging. Findings show that few CSS-related metrics exist, and there is no evidence of proof for their mathematical soundness through the popularly known frameworks such as Briand framework and Weyuker’s properties. In addition, they have not been empirically validated. In order to address this gap, future studies should focus on defining and validating new metrics for CSS and its pre-processors.