Mention what are the main language or platform used for web-design?

It really depends on what you want to do.

php to answer your question but there are additions based on what you need such as;


Style sheets for customization of layout.
Java script to solve runtime needs.
MySQL or any database needs.
Flash optional for interactive flow.

Some of these have multiple options and work arounds.

Check out the profile. With that background advertised , it seems to be a setup question.