Yahoo is changing the way they set minimum bids on paid search. Over the next few weeks they will set the minimum bid based on quality and value rather than how much you pay. The minimum bids will be set by individual keyword.
Yahoo describes the change like setting minimum bids in an auction. So the more valuable, high quality, or demand there is the higher the starting bidding price is.
Previously the minimum bid never fell below 10¢ but with this change you could pay less per click. On the Content Match (your ad showing on web sites instead of with search results) minimum bids will remain at 10¢.
Here’s a breakdown of the factors Yahoo will use to determine minimum bids: