What are different HTML errors?

HTML or hyper text mark up language is perhaps one of the most used mark up languages for the web pages, sites and applications with which most of us are familiar. This language is written using the HTML elements which mainly constitute of the tags enclosed in the angle brackets like:

These elements are housed in the web page or site. Most of the HTML tags are implemented in pairs of two.

HTML ELEMENTS AND CONTENT
- Some tags are even empty and are commonly known as empty elements.
- These are usually unpaired unlike the filled elements which are paired.
- In the paired tags, the first tag is called the start tag and the second one is then called the end tag.
- Between these two tags, any text, comments, tags etc can be added by the designer of the web sites.
- The content that is to be added should only be of textual type.
- Due to some wrong designing principles often some errors are introduced in to the html of the web site or the page.
- One of the most common errors is the insertion of the graphical content in to the html.
- Such content is neither displayed nor is it interpreted.
- It simply causes the malfunctioning of the web site.
- Other elements of the html allow the addition of the graphical content and only these should be used whenever some graphics are to be inserted in to the page.
- Html elements provide a means for the creation of the structured documents that denote the structural semantics for textual content like:

1. Lists
2. Links
3. Paragraphs
4. Headings
5. Quotes and so on.

DIFFERENT HTML ERRORS AND THEIR IMPACT

- Html can also be embedded in to the scripts like javascript which also some times leads to errors when inserted incorrectly.
- Such errors affect the behaviour of the web sites and cause them to behave abnormally.
- Whenever the site is affected by an error or a bug is encountered, a set of error messages is generated by the business logic component which is then stored as a string in any of the available scopes.
- For using such functions, you need to define an application scope with the name of default attribute, because if such a scope is not found, then nothing is to be rendered by the business logic.
- Some designers forget to define such scopes and therefore end up with unnecessary errors in their web sites.
- Many more errors occur whenever a requested is generated by the client to the web server.
- In such cases the server responds with some status messages, few of which have been mentioned below along with the possible errors:

1. 400:
Bad syntax of the request is preventing the server to process it.

2. 401:
The request though being cannot be processed because of unavailability of the authentication processes.

3. 404 not found:
The page requested by the client is found to be unavailable at that moment.

4. 405 method not allowed:
The client made request in such a way that is not supported by that site.

5. 407 proxy authentication required:
The client has not authenticated its proxy.

6. 408 request time out:
The server’s request time expired while waiting for the client to generate one.

7. 409 conflict:
The server is not able to process the request because of the presence of some conflict in it.

8. 410 gone:
The page that was requested is no longer available on the web.

What is Software Architecture ? What are subsystems and interfaces?

Software architecture defines a set of decisions about the organization. It includes:
- how to select structural elements.
- how to select their interfaces.
- how to select the behavior.
- how to select the composition of these structural and behavioral elements into larger subsystems.
- architectural style that guides this organization.
A software architecture is a description of the sub-systems and components of a software system and the relationships between them.
Software architecture is layered structure of software components and the manner in which these components interact.
A software architecture is modeled using package diagram of UML. A package is a model element that can contain other elements.
A subsystem is a combination of package and class. The advantages of defining subsystem are:
- Development of smaller units is possible.
- Re-usability increases.
- Handling complexity is managed properly.
- Maintainability eases.
- Supports portability.

An interface is a set of operations.
- Allows the separation of the declaration of behavior from the realization of the behavior.
- Serves as a contract to help in the independent development of the components by the development team, and ensures that the components can work together.
- There are two styles of communication subsystems use: client-server and peer-to-peer communication.