Hi, I was checking the keywords and the avg. positions for a site in Google Webmaster Tools, but as I returned to Google, the sites were nowhere around those positions after a manual check in Google Search. Or am I getting something wrong? Those are positions in the GWT are the positions in the SERPs, right?
Firstly when you check GWT you will see 48 hours old data. Secondly that's an average data. Let say your site got 3 impression in search results 1st at #90 2nd at #70 3rd at #65 So GWT will show 75 which is not right! If you want to track the sites results the you must use Rank Tracking for your keywords.
I would never use Google Webmasters Tools to track my current rankings. There are a lot of free tools with more accurate data that isn't 2 days behind. Still it has some value since you are able to see impressions, clicks, CTR, etc for each keyword.
Google Webmasters tools show some delayed data. That's why when you check it you will not find your site in result page.
You need to logout of your current Gmail and clear the cookie to have more exact results. or the position can be different at different places, the ranking in us may not be the same as in the uk.
I think this is due to the fact that webmaster tool shows old data and from which data center they generate the result, this is difficult to say. So dont rely much on webmaster ranking statistics. Simply go to google and search with your keywords.