Want To Change The Look Of A Box

[helloworld]

Hello everybody

 

I am trying to modify the looks of boxes. I want a box to have one background color, and the heading should be the same color. So the box should look like a square with the same color everywhere. I managed to make the background color and the heading color the same and removed the image that was at in the left upper corner so now the box looks like a square with the same color everywhere. The problem is that there is still a grey line between the heading and the rest of the box. I need help with removing this line. Can I do it in the stylesheet.css file or do I have to change the source code of the box class? If I have to change the source code of the box class I would like to know where this line is in the code. I have looked in the code already but I can't find the code that makes this line.

 

In general I hear that one should make the changes with css. Am I am able to make most changes in the file stylesheet.css or do I also have to change the source code sometimes? How often does one have to change the source code if one only wants to change the looks of the site but not the funtionality? Any help is very much appriciated. Thanks in advance.

 

Regards

HW