Final answer:
To change the text color to white for every unvisited and visited link within a nav element, use the CSS pseudo-classes a:link and a:visited combined with the color property set to white within a nav selector.
Step-by-step explanation:
To set the text color of every unvisited and previously visited hypertext link within a nav element to white, you would write the following CSS code:
nav a:link, nav a:visited {
color: white;
}
The nav selector targets the navigation section of a webpage, while the a:link and a:visited pseudo-classes select unvisited and visited links, respectively. Setting the color property to white ensures that all links within nav elements have white text, regardless of whether they have been visited or not.