when you zoom your browser with Ctrl + mouse wheel (IE9, FF10, Chrome 23 - so I guess any random browser), GXT grid column lines are not rendered correctly anymore
You can see that in your basic grid example. I attached a screenshot, how it looks (I marked one column line).
In bigger grids it's a bigger problem (10% zoom in is already pretty noticeable).
What version are you using? Can you reproduce it with 3.0.5 at all?
The staging server isn't being used any more, and doesn't get updated regularly. Internal testing builds are mentioned in the forums for quick verification that a bug is fixed, but these move around as we change how we test and what version we are focusing on. Currently there is a copy of 3.0.5 hosted at http://qa.sencha.com:8080/examples-3...lace:basicgrid and the nightly build is at http://qa.sencha.com:8080/examples-d...lace:basicgrid but both of these may change. The most reliable way to check the nightly build is to download it and run it locally.