If a class is reusable, that is to say that it can be used in several different applications, then it has been designed using what good design principle

You can not do so.unless you open another tab in your browser.because you can have up on different tab up to six tabs.i hope this

Well, this code would box the whole body of an html document. by using the relative value for position, you are telling it to position relative to its normal position, which the top left corner is at (0,0). by using left: 50px, you are telling the box to set the left margin  edge to 50px and by using top: 50px, you are telling it to set the top margin edge to 50px. by doing this shifting, the top left corner of the box, which is at (0,0) would be positioned at (50,50)

The correct answer is no.

True.