Microsoft Expression Web provides several ways to check your web pages for code errors and code that's incompatible with particular HTML and CSS schemas. The status bar and Code view alert you to code errors and incompatibility in a single page, while the Compatibility task pane lists all code errors and incompatibility in one or more pages, or an entire website.
Expression Web identifies incompatible code by using a document schema that is based on the DocType declaration in a page. If the page doesn't contain a DocType declaration or the DocType isn't recognized, Expression Web uses a secondary schema. For more information, see Set document type information.
When the current, open web page contains a code error, the status bar at the bottom of the program window displays the Code Error Detected icon ; when the page contains code that's incompatible with the specified DocType, the status bar displays the HTML Incompatibility Detected icon .To highlight the first instance of an error or incompatibility in the Code view of the page, double-click either icon in the status bar or right-click either icon and click Go To Error. To go to the next instance in Code view, press F9.
Expression Web can highlight incompatible HTML and mark invalid HTML and CSS code with a red, wavy underline in the Code view of a page or cascading style sheet (CSS) file. You can point at highlighted or underlined code issues to display a ScreenTip that provides specific information about that instance of code. To go to the next instance of a code error or incompatibility, press F9.
You can turn these options on or off in the Page Editor Options dialog box, on the General tab, under Code View Options. For more information, see Format code.