Well the widths aren't behaving because you have two different sets of padding on them, due to the "th" and "td" classes.
So, anything with the classes "th integer" is going to have a width of 181px and a padding of 10px. This adds up to a total width of 201px
However, anything with the classes "td integer" has a width of 181px and a padding of 20px, which means they have a total width of 221px
So, due to your padding, those are always going to be 20px different from one another.
The reason you have a "right margin" is because the table with class "standardTable" is actually inheriting it's width from the js fiddle window, which means it is 100%. You need it to be set to a fixed with that adds up to all the cells inside.
You can see the problem here:
<div class="th integer">
Podkategorii
</div>
<div class="td integer">
0
</div>
.standardTable .th {
display: inline-block;
background-color: #2b5797;
padding: 10px;
}
.standardTable .td {
display: inline-block;
background-color: #2d89ef;
padding: 20px;
}
Here's a working fiddle:
http://jsfiddle.net/shayl/8z4aw/13/