Thank you for reply!
You're right.
But when converting file to epub it adds tag <border="1"> то images.
It also adds style sheet classes .calibre2 and .calibre7 with background and border to the headings – I can edit in in Calibre editor.
Is there way to avoid adding this tag and style sheet classes?
If Calibre do not adds this tag, is there any way to remove it quickly? I did it manually with editor.
I'm using IOS and mac os iBooks readers – they both render borders etc. It seems, that some reader (including Kindle touch, wich I have also) ignore for some reasons some tags...