Z:gnu-www-ja-fsf-html-style-sheet--592571-In the past, GIFs have had pat/en

In the past, GIFs have had patent problems. However, now that the IBM and Unisys patents (and other patents world-wide that are relevant to LZW compression) have expired, GIFs that are based on the 87a or 89a standard are acceptable. Please be wary of proprietary applications that may include non-standard patented technologies (we'd prefer you use free software applications when authoring for our websites). In general, PNG or JPEG format, are still safe, and are probably better from a technical standpoint. For details regarding the old GIF problem, see http://www.gnu.org/philosophy/gif.html. Other formats are also allowed, though JPEG is the one most widely recognized by Web browsers (be careful with JPEG 2000, as well as PNG alpha channels, as it includes features not fully supported by older browsers).