html - How do you know the location in pix -

I will try and ask if I am not clear then I am very sad.

I am trying to learn CSS and HTML

When it comes to positioning an image, for example top: # px; , How do I know what the pixel space is? Is there a program for this or is it a guessing game?

I hope you understand my question. Thanks

Using CSS is not possible to know the status of an element. It can be done using Javascript. Check it out and

If you know jQuery, it would have been much simpler. Just use

Is there a program for this, or is it a guessing game?

The dimensions of all the elements in your layout.