I found this strange files in my server:

Please can anyone tell me what's that?

Most probably you have Who's online add-on installed, and all of those files appear to be temporary versions of this add-on's data files.

If the system is set up normally, such files should not appear.

It's a very very bad indicator of how your server's file system works. Having such large amount of temporary files could mean there is a big hiss on your server physical disks. As my practice shows, it's better to move to another server, because in the future you could meet other server side problems, even lose database.

Thanks ;)

I emailed them the problem..
they told me this:

You may want to set something up to clear this out, or change the
settings so that the large output is dealt with more quickly. Again, you
would want to check with your developer on this, as these would be
script-side changes. Hope this helps a bit!

Cus I still have same problem..

Who is your developer? :)

I am not wondering they replied you in a "get off" style. The reply is full of not meaningful words.

I already wrote above - the script is programmed to work in optimal mode. Getting instant information about users can't be faster than it's implemented now. We are not going to change the code or give you additional recommendations. This add-on proved 100% to work within years of testing. On our server, it works for years without appearance of temporary files. In your case, it means a bad server.

How much do you pay for the hosting? If it's about $5/month or even less, there is no wonder. Cheap servers always have bugs like this.

And of course, hosting provider never will say they are guilty. Guilty are always programmers. I have passed through this for many years of practice.

Paul
I'm not saying that.. Cus I don't have enough information about these things.. ;)

It's about 9.50 $ per month.
and sharing server.. (DreamHost)

I will check again with them... ;)
Thanks

Ok, I think I answered your question.

The reason these files are left, is because tempnam command of php doesn't work properly for some reason. Dig the hoster on this point.