Can I delete links to schemas.microsoft.com?

Various SharePoint 2010 master pages contain lines such as:

xmlns:ddwrt="http://schemas.microsoft.com/WebParts/v2/DataView/runtime">

If I try to visit the URL mentioned, I get an error message about the page having been moved or deleted.

Does this mean it's safe/advisable to delete all those xmlns ddwrt lines from the master pages?

I'm trying to tidy up our sites, and also clean up any non-https links.  It appears to me that these links to schemas.microsoft.com are doing nothing.  Am I correct?  Can I remove them?

Rob Schifreen SharePoint 2010 Admin University of Brighton, UK