MODx parse error??

After making a simple change to some data on a page and pressing save this error message has come up and now we cant access our site or edit it.. how do we fix it?(in as much detail as possible please)

« MODx Parse Error »
MODx encountered the following error while attempting to parse the requested resource:
« Execution of a query to the database failed - Table './leftba69_leftbank/modx_site_content' is marked as crashed and should be repaired »
SQL: SELECT sc.* FROM `leftba69_leftbank`.`modx_site_content` sc LEFT JOIN `leftba69_leftbank`.`modx_document_groups` dg ON dg.document = sc.id WHERE sc.id = '1' AND (sc.privateweb=0) LIMIT 1;
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Parser timing
MySQL: 0.0024 s (0 Requests)
PHP: 0.0134 s
Total: 0.0158 s

If you have PHPmyadmin, go to your table listing, select all and hit 'repair' in the dropdown menu. See attached screenshot.