If we edit a wikipedia page and we add some wrong information in that page,will it be deleted by wikipedia?

It remains until someone else flags it. Some stuff is examined and caught but other stuff is not. This is the flaw with Wikipedia. This is also why no real papers, articles, books, etc., will accept Wiki as a source of reference. It can be a good starting point, but you can't really take it as true encyclopedia replacement.

I read a news story today that they are tightening the rules because somebody edited Senators Ted Kennedy & Robert Byrd's pages to show they were dead. In a few weeks, all edits made by anonymous or unregistered users will have to be approved by a registered user before its added. http://tech.yahoo.com/news/afp/20090126/tc_afp/usitinternetwikipedia_20090126194940

When I see such a thing, my tendency is to revert it quickly. It's against Wikipedia's policies against misinformation. We require sources to be posted along with that information. Else, it gets removed.

No other people will edit it

If you are to edit something, and spam or add something wrong, most likely, if it's spam, they will post it, and delete it and revert it back to it's original form immediately, and if you do something wrong, the same, but sometimes, if they think it's correct, it will be posted, but will remain wrong until someone changes it back.

the website has moderators

Although reggae music might not be your genre of choice, every musical genre has its stars. A Wikipedia article on one famous reggae star now deceased was deleted by persons unknown and her family are having problems getting it put back because Wikipedia claim it is still there. A search on her name which used to take you straight to the page now comes up "No article found". For this reason I now have no confidence whatsoever in the integrity of Wikipedia. They do not seem to know what they are doing.