[Home](./index.md) > [puppeteer](./puppeteer.md) > [CSSCoverage](./puppeteer.csscoverage.md) > [\_onStyleSheet](./puppeteer.csscoverage._onstylesheet.md) ## CSSCoverage.\_onStyleSheet() method Signature: ```typescript _onStyleSheet(event: Protocol.CSS.StyleSheetAddedEvent): Promise; ``` ## Parameters | Parameter | Type | Description | | --- | --- | --- | | event | Protocol.CSS.StyleSheetAddedEvent | | Returns: Promise<void>