Duplicate content reported in Webmaster Tools

[smallcompany]

I've been fixing this for a while now. Three cases:

1. a case where a link with Google AdWords' GCLID appended showed up and got reported as a dup of identical page
2. a subfloder being a dup of index.html
3. a case where I moved pages into a subfolder and implemented proper 301 at the same time

My comments:

1. I understand that the query string may mean a different page, so no wonder, you have to figure how to fix such things - yourself.
2. Here I would expect Google to figure that those two are the same thing, but again, you fix it by being careful how you link throughout your site, and you implement a redirect index.html > folder or vice versa, whatever you want.
3. This one I cannot help because the moment when I moved the pages around was the same moment when I copied over the new .htaccess with the new 301 rules. It's almost like the WMT is aggregating stuff from two or more Google servers that carry different data for a single site.

Have you been seeing more of stuff under HTML Suggestions tool lately?

Thanks

[Receptional Andy]

If you see dupes listed of redirects, then it's just a temporary thing. Google never indexes the new URL and old location at the same time, so any time you redirect a batch of pages you're likely to see duplicates. It's one of the hazards of URL migration.

You can fix all of these either with the "brute force" method of permanent redirection (which I always prefer if available), the canonical attribute, or, as a last resort, the "parameter handling" options in Webmaster Tools.