Updating height of the rows in tables with jQuery
The only think I can think of to make it perform better is to store the jQuery objects and heights in variables:

var rightTr = $(".superBlock div.right tr:visible");

$(".superBlock div.left tr:visible").each(function(i){
    var leftRow = $(this),
        leftRowHeight = leftRow.height(),
        rightRow = rightTr.eq(i);
        rightRowHeight = rightRow.height();

    if (leftRowHeight != rightRowHeight){
        if (leftRowHeight &gt; rightRowHeight){
            rightRow.height(leftRowHeight);
        } else {
            leftRow.height(rightRowHeight);
        }
    }
});


You could simplify the if-else statement a little, though I don't think you'll realistically get a performance boost:

$(".superBlock div.left tr:visible").each(function(i){
    var leftRow = $(this),
        leftRowHeight = leftRow.height(),
        rightRow = rightTr.eq(i);
        rightRowHeight = rightRow.height();

    if (leftRowHeight &gt; rightRowHeight){
        rightRow.height(leftRowHeight);
    } else if (leftRowHeight &lt; rightRowHeight) {
        leftRow.height(rightRowHeight);
    }
});


The big hit to performance is the repainting and reflowing of the page that results from changing the row heights. If there really is a performance problem with resizing the table rows, then you could dive a little deeper into some enhancements.


Figure out the height of the right table
In the left column, insert a DIV before the table. Give it the same height as the right table
Set the width attribute on the left table to it's current width in pixels
Change the position of the table to absolute so that the table is in its own document flow
Resize the rows
Remove the absolute positioning and width attribute
Hide the placeholder DIV


You should get a slight speed boost by making the table position: absolute while the row resizing gets done because the browser only has to reflow the TABLE element on screen, and not any surrounding elements, but really, this might not buy you very much unless the table is big.