my question is my topic how can i change the links xxx.jpg.html to xxx.html

Can't be done in zenphoto. You can change the "ending" to anything you want in the gallery options, but the image name must stay intact.

The reason for this is because, how else would we identify which image to load? It needs the filename.

We could infer it without the extension, but then you run into conflicts with different filetypes (eg, image.jpg and image.gif in the same directory). We won't be worrying about that right now.

i see this property a lot of sef based gallery script.As far as it must be done while beginning to coding zenphoto.Ok,is this a important thing in therm of seo?

It's important to have some non-image extension to the URL, such as '.php' or '.html' so search engines don't get confused. Otherwise it is not a problem to have '.jpg' before that.

so if i'm using only jpg format pictures is there a method to do this?And is there any inconvenience for the future if i use only jpg formats?

Zenphoto does not provide you with any means to do this for the reasons stated above. You would have to change the Zenphoto code if you wish to drop the .jpg. Why is this such an issue for you? You can certainly add a suffix to the images as trisweb has suggested which should solve any real problems.