Advertisers currently have the choice of providing a long, 190-character ad description or a short 70-character version. However, starting in May, the short version will be required and the long text ad will be optional.
At present, long descriptions get automatically truncated, usually at the last full-stop before the 70th character. This isn’t optimal, as some ads may sound incomplete if the copywriters did not realise the ad would be cut off at that punctuation mark.
Only some Yahoo! partners still show the long description. The Yahoo! sites changed to the 70-character description earlier this year.