Sometimes when I search my keywords to see where my website is ranking in yahoo, the website ranks highly, but then I will search another time and there will be double the amount of results and my website will not appear at all. Is this common with yahoo?
yeah you are right its a problem with Yahoo.without reason you got high search result and then got low
Last month on yahoo search blog there was an official note that Yahoo begins testing with microsoft. In that they said that the listing on yahoo were coming from results powered by Microsoft. After Yahoo! and Microsoft search Alliance they are doing all these things. So we will have to wait for their next update on this which clarifies the behavior of SERP's.