[dubir]

[Bubbaloo]

Looks like reflected caustics.

[dubir]

can you advice how can i avoid it ?

[Bubbaloo]

What does your glass material look like?

[Mihai]

You could set the glass of that panel to be hidden from reflections and it won't get reflected in the floor. If that is the problem...more info here about these options:
http://support.nextlimit.com/display/ma ... visibility

[Fernando Tella]

Probably it comes from the green framed glass behind the chair.