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I have to say I agree with Sha on this one.

If you are not confident in using .htaccess then I wouldn't bother. I think there is a much easier solution:

1- As Sha said, use webmaster tools to tell Google how to handle these parameters, this should slowly start to take them out of the index.

2- Add rel=canonical to all your pages, this way even if parameters are added, the rel=canonical will always point back to the original and remove any risk of duplicate content.

I hope this helps.

Craig

Hi Oliver,

The blue notices are only there to highlight things that you might want to be aware of. These are not always bad things and looking at your site, it looks like you have implemented it correctly. The notice is really just to remind you that the rel=canonical is there in case you were not aware or you are auditing a clients site that you don't have experience with.

Craig

Hi Simone,

It sounds strange that you can access the pages ok but Moz crawl says 404, however, as James said, the process for for fixing 404 errors is to add a 301 redirect to the correct page. If the content is old or no longer there, 301 it to a related page and finally if that isn't an option 301 it to the home page.

Another good way to check what pages Google is getting a 404 on is by signing up for webmaster tools if you haven't already. You can then look in the crawl diagnostics and see 404 pages.

Hope this helps