Google was showing up pages with affiliate ID parameter in the search results. After some research on how to disallow this, I came across URL parameters in Webmaster tools. I set the parameters for ?a_aid= to Representative URL/No, doesn't affect page content. It's been two weeks since I made the change but Google still shows these results and in Webmaster Tools in the "Effect" column it still shows "None."
How long should I wait for the changes to take effect?
"Effect": "None" doesn't mean that it isn't working. That means that the parameter has no effect on the output of the page. If you set "Crawl" to "Representative URL" then "Effect" automatically becomes "None" (and stays that way forever). If you set "Crawl" to "Every URL", then "Effect" becomes "Specifies".
You will know it is working when Googlebot stops crawling pages with that URL in it, and when those pages disappear from the index. I believe crawling should have stopped within a few days of making that change (check your server logs to see). It may take a few weeks for all of those pages to fall out of the index once Google stops crawling them.
