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.
