I want to put a table in my content bar, but in some screens the table is over the right sidebar. I use a simple table, copied from word, no photos or anything else included.

you should never copy anything from a word document and paste it into a post. Word has embedded code that messes things up.

there is a 'paste from Word' icon in the post editor you should use to strip the embedded code.

This is what I mean, that I copy it with the special button.

What is the url

http://potohori.gr/2012/09/09/test/ this is the link when I have a simple table.
http://potohori.gr/2013/02/20/poll3a/ this is the link when I put the table in Contact Form 7 (this is what really interests me now.
When I use my laptop wchich has a good screen 15'6 chrome or IE everything is ok. With older pc's though there are problems. Probably I have to put a code that resizes the table.

you need to remove all the embeded styling in the table. For example change

<td valign="bottom" nowrap="nowrap" width="261"><b>ΥΠΟΨΗΨΙΕΣ</b></td>

to

<td><b>ΥΠΟΨΗΨΙΕΣ</b></td>

This partly fixed the problem. Now I don't have problem with the right sidebar, but since there is no wrap when I see smaller screens the names and everything else go vertically

Can anybody help me please??

the only way I can see you getting that extremely wide table into the space provided it to redcue the font size to something you probably can't read. You may want to rethink your design.