Duplicate Content, duplicate title tags, duplicate titles or duplicate keyword are a no no to Google and hence to your page ranking and traffic.
Recently When I checked my site in Google Webmaster tools, I found to my horror that there were like 12 URLs with duplicate tile tags in HTML suggestion section.
Lets see how we can solve this problem. The issue with duplicate title tags was that the mobile version of the URLs with ?m=0 are being indexed and so Google sees two URLs with same content and title. See below.
So when I did some Google search, I found out there are two ways to solve this problem. Canonicalization and edit URL parameter settings.
You can set your preferred URL, among different versions of it, to be Canonical. For which you have to add this tag in your head section of that page.
<link rel="canonical" href="http://www.example.com/abc/xyz.html">For more info, here is link from webmaster tools help. https://support.google.com/webmasters/bin/answer.py?hl=en&answer=139066
But if you are lazy like me, then you can have the second option. Now go to webmaster tools and select your site and then select "Site Configuration" then "URL Paramaters". Add a parameter, in my case 'm', then tell what googlebots should do with it.
Here is the link from Webmaster tools help which explains every options so that I don't have to do it again. https://support.google.com/webmasters/bin/answer.py?hl=en&answer=1235687
Before going any further, I got to remind one thing to you guys. Use these options carefully, so read and understand every options before choosing it. Because if you do it wrongly, you may end up removing many pages from Google indexes, valid non duplicate pages!
So I checked and confirmed that 'm' parameter is just for mobile version and I choose "No URL" option. After like 4 to 5 days the duplicate title tags error message was gone. And also I verified the number of indexed pages before and after doing this URL parameter thing. It went through fine, for ME atleast!
Good Luck guys.
But Don't come and complaint if you happen to see some change in the number of indexed pages. Do it with your own risk.