An external style sheet is simply a text document that contains style rules. External style sheets have a .css extension.The <link>element lets you establish document relationships. It can be used only within the <head>section of a document. To link to an external style sheet, add the <link>element as shown in the following code:<head><title>Sample Document</title><link href=“styles.css” rel=“stylesheet” type=“text/css”></head>The <link>element in this code tells the browser to find the specified style sheet. The href attribute states the relative URL of the style sheet. The rel attribute specifies the relationship between the linked and current documents. The browser displays the Web page based on the CSS display information.The advantage of the external style sheet is that you can state the style rules in one document and af-fect all the pages on a Web site. When you want to update a style, you only have to change the style rule once in the external style sheet.
PTS:1REF:153-1563.What are the four basic selection techniques? Briefly describe each technique.