Your sidebar is too small.

The default theme requires quite a bit of space. Depending on the 
language you're using, you may need more than the default of 210 pix. 
For instance, in Dutch you'll need at least 240 pix, so that the 
translations of the menu fits in the allotted space. I did this system 
wide (since all my users use the Dutch locale) by setting

<?php
$_prefs['sidebar_width']['value'] = 240;
$_prefs['sidebar_width']['locked'] = true;

in 'horde/config/prefs.local.php'.

Here is a screenshot. I upgraded to latest PHP5.3. But the issue is 
still there.

Looks fine here. Which FF version, which platform? And can you post a 
screenshot?

Had to set margin and padding to 0px

/* Mini calendar */
.kronolith-minical {
     position: relative;
     margin: 0px;
     padding: 0px;
     background-color: #d5dcde;
}