Wikipedia is basically an encyclopedia, so sometimes they won't publish an article if they feel like it doesn't belong there. It's almost like someone trying to publish an article about themselves, it won't let people do it.
Pages and media that satisfy certain criteria are speedy deletion candidates, which means that they can be deleted immediately and without discussion. The criteria include pages that contain nonsense, copyright violations and articles that do not satisfy notability guidelines. When deleting these, administrators often leave short codes in the deletion summary instead of typing out a full reason, such as "A7" for articles that do not satisfy notability, or "G1" for patent nonsense. These codes are explained at criteria for speedy deletion.
Articles (but not other pages or media) may be proposed for deletion by any editor. If nobody objects to this within five days, the article is deleted. If any objections are raised, the article is not deleted, but anyone may still make the matter the subject of an Articles for deletion discussion (see the next section). Proposed deletions will often be labeled as "prod" in the deletion summary.
A page or media file may also be nominated for consideration in a deletion debate, so that editors can discuss whether it should be deleted. Articles are discussed at Articles for deletion; other pages elsewhere (see Deletion debates for links). Such discussions normally last five days, after which time an administrator will delete the page if there is a consensus to do so. Anyone may participate in such a debate, however these discussions are not "votes". The weight of an argument is more important than the number of people making the argument, so encouraging mass participation in such debates to avoid the deletion of a particular article will not work.
If a particular page has been recreated and deleted multiple times, administrators may decide to protect it so that it stays deleted. If you try to edit a protected title, a message box will inform you about it.
What you can do about it
If a page or file that you created has been deleted, please don't take offense. See our content policies and the guide to creating your first article to get an idea of what you should be aiming for. Alternatively, remember we already have 2,637,335 articles – find a subject that interests you and work on improving our existing content.
Depending on the reason why the page was deleted, there are also several ways you can try to have it undeleted by administrators. In every case, you should first make sure that the page is appropriate for inclusion in Wikipedia and, if it is an article, that its content is based on reliable sources. If it is not, your request will likely be unsuccessful.
If you feel a page has been deleted in error, or if you think you have good reasons for wanting to edit a protected title, first contact the administrator responsible via the method explained above. If you are still not satisfied after discussing it with the deleting admin, consider starting a deletion review.
If an article was deleted as a result of a proposed deletion ("prod"), any administrator should normally restore it on your request. In such cases, you can leave a message on this noticeboard.
If the page was deleted for any other reason, and you would like to be able to access the text (for example, to resubmit it in a form that meets our content policies), there are some administrators who may provide you with the content of the deleted page on your request.
If anything about this whole process remains unclear, ask for help on the Help desk.
A substantial number of new articles by new users end up getting deleted. If you are one of those new users, you may feel confused right now, and need to ask for help on the Help desk.
If it looks like your page is definitely about to be deleted, copy-and-paste the source code to a text file, for example by using a text editor (which preserves your wikitext markup), or a word processor. However, after your page is deleted from Wikipedia, do not immediately put the page back up! Otherwise, it will probably just be deleted again, and the page name may even be protected against re-creation. Either find more evidence to prove the notability of your article, or wait for more evidence to be published elsewhere in reliable sources. If you intend to put your article back up straight away, make sure to post some questions on the Help Desk to ask how you can improve the article the next time around (though, it did get deleted, and that probably means that there is not much that can be improved, or some serious research will be necessary to find those all-important reliable sources your article needs.) You can also discuss how to develop your article properly on the drawing board. If your page gets deleted before you can copy its source code, however,