The hardest job of a Web Designer is to program his web pages in order that they seem the same if visited by using different browsers; the term cross-browser has existed since web development began but not everyone knows about it.
If you browse using Google Chrome, you will notice sometimes, that objects such as html-form buttons, text fields and tables have nice rounded corners, but when browsing the same pages using Microsoft Internet Explorer Browser, you would see just sharp-edged corners in the html objects, and in that case, these are not rendered in the same way, as a Web Designer would have intended.
In that case we would say that round corners relative code [i.e: border-radius parameter] is not cross browsers related to Microsoft Internet Explorer and Google Chrome, i.e. that code is not executed by Microsoft Internet Explorer browser.
While web design could miss round corner enhancements, it surely cannot miss more important HTML feature properties.