A tag is a keyword or label that categorizes your question with other, similar questions. Using the right tags makes it easier for others to find and answer your question.

Cross-posting refers to posting the same question on multiple websites.
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about the quarterly creative commons data dumps of all public data in the Stack Exchange network Q&A sites.
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The Stack Exchange Data Explorer (SEDE) allows you to create and run queries against copies of the databases of popular Stack Exchange sites.
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For questions about posts, deleted by their owners, through automatic processes, or by moderators.
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the tag to use for any questions related to deleted answers specifically.
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refers to all questions deleted from Stack Exchange sites. The tag "specific-question" should also be used when referencing a specific question that has been deleted.
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"Design" refers to front-end elements, such as page layout, coloring conventions, etc.
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for questions specific to down-votes, the community's way of telling peers that their content can be improved. Down-votes on meta site have different meanings.
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referring to the process of identifying and closing questions that are duplicates of another question.
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a core, fundamental Stack Exchange value; we allow editing by registered and unregistered users (if peer reviewed).
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enter Stack Exchange posts, which supports a live preview of Markdown syntax.
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held to choose moderators for graduated sites.
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the norms and standards of accepted behavior and politeness in our community. The golden rule is "Think before you post."
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referring to the process of identifying and closing questions that are exact duplicates of another question.
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For questions about the flagging process, how flags are handled, etc.
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fun! Use this tag for anything that suggests adding a new layer of gamification to the site.
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For questions concerning Google, a popular search engine and the main referrer to Stack Exchange sites.
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For issues regarding the help center of Stack Exchange.
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Relating to the discussion and controversy around questions that are explicitly stated as, presumed, or suspected to be homework questions (i.e. those given to a student in a formal course of study).
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HTML links, generally those created within the network on questions, answers, or the site itself.
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For questions about the images used in your own posts.
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a set of tags that can be marked by a user. The questions that have favorite tags will be highlighted, and can be monitored using Tag Sets.
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for questions regarding the process of reviewing improved code over time.
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Legal issues, including copyright, licensing, patents, and trademarks
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Questions about the licensing of content on Stack Exchange sites.
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For questions regarding locked posts and locking functionality. Diamond moderators can lock a question or answer.
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for questions or issues surrounding login to this site.
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