Probably unwanted behavior of the search box

While using Web Style Guide for the Ubuntu-it website, I noticed that on Chromium a strange "x" appears on the search input when a value is provided.

After some investingations, I found that Chrome/Chromium and probably IE (I don't want to start it) appends a very ugly "x" in the right edge of all <input type="search" ...>, which is used to clear the input.
It doesn't happen on Firefox, or other browsers.

If you want to fix that, here is the css snippet for webkit:
input[type="search"]::-webkit-search-decoration,
input[type="search"]::-webkit-search-cancel-button,
input[type="search"]::-webkit-search-results-button,
input[type="search"]::-webkit-search-results-decoration { display: none; }

And this (untested) for IE:
input[type=text]::-ms-clear { display: none; width : 0; height: 0; }
input[type=text]::-ms-reveal { display: none; width : 0; height: 0; }