Like what do you actually mean?
The idiomatic way to create webpages, in this day and age, is to try to separate content of a page from how the browser presents it.
HTML is for the content and structure of a page. CSS is for controlling how it's displayed. The <center> tag is an HTML tag that only exists to control how a page is displayed.
In case you're wondering what to use instead, adding 'margin: auto;' as a css rule will do the trick.
Which is why "modern" frameworks like bootstrap still encourage grid layouts using explicit width classes like span3?
Face it, we haven't gotten any better since Mosaic.