See Peer review for incisive, constructive criticisms from others on a finished article.
See MediaZilla to make wiki software bug reports and feature requests.
See Alternate Sites For When The Main Wikipedia Server Is Down You should bookmark the sites noted because once Wikipedia is down, you won't be able to access this page.
IF YOU HAVE REALLY MESSED UP A PAGE, and accidentally saved it, simply click on the history tab (at the top) and then click on the date immediately preceding that of your change, then click on edit this page, then save the resulting page. This will revert the change.