Standards-compliant

Standards-compliance is the compliance of a website or web browser with the web standards of the World Wide Web Consortium (W3C). To ensure interoperability a standards-compliant web site does not use proprietary software methods or features of a browser.
Although there is no perfect browser that adheres to all standards, advancement has been made by most web browsers in the past few years that will ensure better interoperability. In the past a "standards-compliant browser" sometimes meant "a browser other than Internet Explorer" (which had poor compliance prior to the release of version 8.0 in 2009).
Current use of the term "standards-compliance" generally refers to the adherence to coding practices in relation to the use of HTML or XHTML, with Cascading Style Sheets (CSS) to define the layout, colors, and fonts of a web page.
Purpose.
Modern web browsers currently under development, or recently released (Opera 10, Mozilla Firefox 4, Microsoft Internet Explorer 9, Safari 5, Google Chrome 5) fully support the CSS 2.0 standard, as well as some of the CSS 3.0 standards.
See also.
Public standards compliance tests: