Originally Posted by ankifreeze
I usually make experiment don't need care about another element that have no relation of my experiment.....
Well, the irony of your statement is that sometimes things like unclosed elements do
have a relation to anything you experiment with. First rule of web development (or any
programming related task, if I may say): You canít expect proper results from invalid code. For example if you have no doctype the page may display significantly different than with a proper doctype. If you donít close elements then this will result in nesting errors and Ė depending on the capabilities of the browsers to handle code errors Ė in erroneous display of your experiment.
So, keep this in mind: Always make sure your code is standards compliant and error free!
Every experiment has to be well prepared. Why do a bad job if you can do a good job?