The View Source feature in browsers allows users to see the raw HTML source code of a webpage. Even if content is commented out using HTML comment tags, it is still visible in the source. This is a key consideration for developers to ensure sensitive information is not left in comments. 

In HTML, comments are wrapped between . These delimiters instruct the browser to ignore everything between them. It's important to note that unlike comments in some other languages, HTML comments are visible in the source code but won't be displayed in the rendered page. 

The shape attribute in the

tag is used to define the shape of the clickable area in an image map. The possible values can be "rect" (rectangle), "circle", "poly" (polygon), and "default". This attribute, in conjunction with the coords attribute, enables different areas of an image to be linked to different destinations. 

The line-height property in CSS determines the amount of space above and below inline elements. It's typically used to improve the readability of text, especially in larger blocks. The value can be a number, length, or a percentage. When used correctly, line-height can enhance the visual appeal of text on a webpage. 

Using appropriate heading tags (h1 through h6) in HTML provides a structured hierarchy to your content, making it more readable for both users and search engines. This structure helps search engines understand the importance and context of the content, which can contribute positively to search engine rankings. Proper use of headings can enhance content discoverability and accessibility, thus playing a crucial role in SEO. 

Commented out code doesn't execute or affect rendering. If a script tag is commented out, any functionality provided by that script will be unavailable. To truly understand its effect, one would need to uncomment it and observe potential behavioral changes on the webpage. 

In HTML, a description list is represented using the

tag. Within this list, the

tag is used to denote the term, and the

tag is used for the corresponding description. Description lists are useful for things like glossaries or key-value pairs. 

The

tag is not directly associated with tables. Instead, it's used with the

element to provide a visible heading for its content, making sections of content expandable and collapsible. This can improve user experience by letting users choose which sections they want to see, reducing information overload. 

The

element is utilized to group the body content in a table and works as a container for one or more

elements (table rows). While

defines a row, the

helps in structuring the table and can be particularly useful when working with styles and scripts, as you can apply styles or perform actions on this grouped content. 

The target attribute specifies where to open the linked document. When set to _blank, it ensures that the linked document is opened in a new tab or window. It's often used when linking to external sites to keep the original page open in the background.