In an advisory on the Yahoo Search Marketing Blog, Yahoo has told advertisers they need to tighten up their ad copy.

Yahoo is taking away the longer, 190-character ad option and requiring all ads be made up of 70 characters or fewer. The change will be effective beginning in May. When creating new or modifying existing ads, advertisers will see only the shorter option.

Advertisers have until June to modify existing ads longer than 70 characters or risk having them cut off in Yahoo Sponsored Search Results. Having the ad cut off, Yahoo warns, can lead to lower returns and a decreased Quality Index Score.

Yahoo says it's making the change to improve the search experience for all parties involved, especially the searcher.