XHTML

Hi
I just wanted you to know that there is one tag that gives everyone problems 
with is the <br/> seems that netscape and exployer 6.0 does not like. I'm 
taking a free on line XHTML course I have tried to explain to all the new 
people that it seems to be a broswer problem.I wish that there was one simple 
language to do basic website design for example XML I like it because it is 
easier and more powerful than HTML or XHTML is there a reason why that we 
cannot have one language that can do all?
                                        
                                            Thank You
                                      Michael A Beach