Q:

what is wrong using  and separation of logic

I got a comment for my question form Tobia Tesan but I can't msg in here.
php echo vs return, which way is better?
He suggest me change to <span class="wuuk_time"> instead of using <b>, which you'll define in a CSS file, thus achieving separation of database logic, output logic and presentation/styling.
First, what is so bad about using <b>?
Second, how do you separation of database logic, output logic and presentation/styling? I use CSS. is that not separation of logic and output?

A:

It's a matter of 'best practices'. Avoiding inline styling, such as the use of the <b> tag is done to improve readability. You can then reuse the class "wuuk_time" throughout your HTML later, as you see fit.
Moreover, if you would like to change the styling to italicized instead of bold for example, it would be easier to change the "wuuk_time" class to reflect your desired changes throughout the webpage as opposed to hunting down all the individual <b> tags in your HTML.
Readability, Maintainability.

