not all BlackBerrys have the same browsers.
They all have the "internet browser" unless you are on a BES and your IT admin removes it.
If you are on a BES you can have access to the "BlackBerry Browser" unless again the IT admin removes it
There is also a "Hotspot Browser" on WIFI capable BlackBerry's only. Again can be removes by IT admin if on a BES
Then there is an "MDS Browser", not used very often and also put on or not, by an IT admin on a BES
Then finally there is the WAP browser, strictly used to access your carrier related sites.
The main 3 browsers, "internet", "BlackBerry" and "Hotspot" all have the ability to emulate Firefox, Internet Explorer or BlackBerry. FF and IE will emulate that you are actually using a PC rather than your device. The BlackBerry emulation is what you should use on your device as it registers mobile sites, removes advertisements, that kind of stuff.
My site works 100% in the "BlackBerry Browser" using BlackBerry emulation, with column view selected. And as mentioned above it is ugly and out of place due to it not have a mobile version. This is where the CSS would come handy to create the mobile version.