I've tried searching with a couple of basic tags under the default(alphabetical order). It seems like the alphabetical order goes as follows: symbols -> numbers -> alphabet letters.
However before this order starts, there's always a couple of results that remain on top which don't conform to the alphabetical sort order.
*This latter search result gives me about a dozen random results, all starting with different alphabet letters, before the actual order starts
In addition, pressing "next page" instead wipes the search results.
I'm on Mozilla Firefox, by the way.
Hope this helps.