Content Security Policy (CSP) is a security mechanism implemented in web browsers to prevent cross-site scripting (XSS) attacks and other types of injection attacks. CSP allows website operators to define a policy that determines which resources can be loaded from a website and from where they can be loaded.

The CSP policy can include various types of restrictions, including:

1. Allowed sources for scripts, images, stylesheets, fonts, and other resources.
2. Restrictions on the execution of inline scripts and inline styles.
3. Setting security policies for specific types of resources, such as enabling HTTPS or using non-trusted HTTP sources.
4. Reporting mechanisms to receive reports on violations of the CSP policy.

By using CSP, website operators can reduce the risk of XSS attacks by restricting the execution of unauthorized code. However, developers need to carefully ensure that the CSP policy is configured properly, as a too restrictive policy may potentially impact legitimate functions of the website.

LESS is a dynamic stylesheet language developed as an extension of CSS (Cascading Style Sheets). The name LESS stands for "Leaner Style Sheets," indicating that LESS provides additional features and syntactical improvements that make writing stylesheets more efficient and easier to read.

Some of the main features of LESS include:

1. Variables: LESS allows the use of variables to store values such as colors, fonts, and sizes and then use them at various places within the stylesheet. This greatly facilitates the maintenance and updating of stylesheets.

2. Nesting: LESS permits the nesting of CSS rules, improving code readability and reducing the need for repetition.

3. Mixins: Mixins are a way to define groups of CSS properties and then use them in different rules or selectors. This enables code modularization and increases reusability.

4. Functions and operations: LESS supports functions and operations, allowing for complex calculations or transformations to be applied to values.

LESS files are typically compiled into regular CSS files before being used in a webpage. There are various tools and libraries that can automate the compilation of LESS files and convert them into CSS.

Websockets are an advanced technology for bidirectional communication between a web browser (client) and a web server. Unlike traditional HTTP connections, which typically work in a unidirectional manner (from the client to the server), Websockets enable simultaneous communication in both directions.

Here are some key features of Websockets:

1. Bidirectional Communication: Websockets allow real-time communication between the client and server, with both parties able to send messages in both directions.

2. Low Latency: By establishing a persistent connection between the client and server, Websockets reduce latency compared to traditional HTTP requests, where a new connection has to be established for each request.

3. Efficiency: Websockets reduce overhead compared to HTTP, requiring fewer header details and relying on a single connection instead of establishing a new one for each request.

4. Support for Various Protocols: Websockets can use different protocols, including the WebSocket protocol itself, as well as Secure WebSocket (wss) for encrypted connections.

5. Event-Driven Communication: Websockets are well-suited for event-driven applications where real-time updates are required, such as in chat applications, real-time games, or live streaming.

Websockets are widely used in modern web applications to implement real-time functionalities. Using Websockets can make applications faster and more responsive, especially when dealing with dynamic or frequently changing data.

Horizontal scalability refers to a system's capability to handle increased workloads by adding more resources or hardware components, enhancing its performance. In contrast to vertical scalability, where performance improvement occurs by adding resources to a single node or machine, horizontal scalability scales by adding additional instances of resources that work together.

Typically, horizontal scalability means the system can distribute loads across multiple machines or servers. Cloud computing platforms are often designed to offer horizontal scalability, allowing resources to be dynamically added or removed as needed to enhance performance and availability.

An example of horizontal scalability is expanding a web server by adding more servers to better handle user requests, rather than just increasing the resources of the existing server.

Vertical scalability refers to a system's ability to handle increasing or decreasing workloads by adjusting its resources. In the context of computer technologies, vertical scalability generally means enhancing the performance of a system by adding or removing resources within the same hardware.

In contrast to horizontal scalability, where capacity is increased by adding more machines or nodes, vertical scalability involves improving the capability of a single device, such as a server or a database, by adding more resources like CPU, RAM, or disk space.

Vertical scalability provides a relatively straightforward way to enhance a system's performance. However, there's a limit to how much a single device can scale, constrained by its physical limitations. In some cases, scaling might hit the boundaries of the hardware, leading to bottlenecks. This is why many companies also opt for horizontal scalability to make their systems more robust and resilient.