into a : is it correct?

Answer 1

This will work in quirks mode, but the browser which is compatible with standard mode will not work depend upon your doctype. Avoiding quirks mode is one of the keys to successfully producing cross-browser compatible web content

Some modern browsers have two rendering modes. Quirk mode renders an HTML document like older browsers used to do it, e.g. Netscape 4, Internet Explorer 4 and 5. Standard mode renders a page according to W3C recommendations. Depending on the document type declaration present in the HTML document, the browser will switch into either quirk mode or standard mode. If there is no document type declaration present, the browser will switch into quirk mode.

http://www.w3.org/TR/REC-html32#dtd

JavaScript should not behave differently; however, the DOM objects that JavaScript operates on may have different behaviors.