Last updated: 10 July 2016
While plain text editors such as Windows Notepad can be used to write HTML Markup, those that provide more sophisticated editing features (often including writing CSS, PHP, XML, JS code, etc.) are favored by most Web Page authors.
I personally use HTML-Kit 292 (including Download) which is a free Web page Editing/Authoring facility that provides the following features:
Note: Some text editors (Windows Notepad included but not HTML-Kit) insert UTF-8 signature (BOM) characters at the beginning of Markup coding (just preceding the Doctype) as a Unicode description marker. These characters must be removed when generating UTF encoded pages in order to preclude failed validation and Browser display of a blank line (sometimes with various characters) at the top of the web page. Visit W3C FAQ: Display problems caused by the UTF-8 BOM for detailed information including removal procedures. You can check pages to see if they begin with a UTF-8 (BOM) signature via Richard Ishida's UTF-8 BOM tester utility.