 In 1998, Opera 3.5 was released, adding Cascading Style Sheets (CSS) support and file upload capability.Since version 3.5, Opera has supported CSS, and Håkon Wium Lie, one of the inventors of CSS, is the CTO at Opera.Up to 6.0 Opera supported most common web standards, Netscape plugins and some other recent standards such as WAP and WML for wireless devices, but its implementation of advanced ECMAScript (of which "JavaScript" is an implementation) and the HTML Document Object Model was poor.