Messing borders while resizing window

[Voorm]

Hello.Each time when i resize window i get mess.What i should add in css?And how to make #body to be midle of schreen always?Here's some codes:

<div id="body"><div id="manu"></div></div>

body{font-family:Comic Sans MS , Arial;text-align:center;background-color:#000000;color:#179161;cursor:help;}#body{width:700px;height:600px;border:2px solid #179161;box-shadow: 30px 20px 35px #4A804E;position:relative;}#manu{width:600px;height:100px;border:2px solid #179161;margin-top:1mm;margin-left:50px;position:relative;}

[niche]

Have you looked at it with your developer tools?

[Voorm]

Only 2 develop tools i using,and it's xampp & notepad++And testing always in 4 browisers from localhost.Elastic container is something what i curently can't understand.When i say elastic i say while resizing window or etc to it keep own positions.(i using 1024x768)So,if i change in another size,it change a litlle.

[dsonesuk]

With horizontal alignment you would use margin: 0 auto; on both #body, and #manu

#body{width:700px;height:600px;border:2px solid #179161;box-shadow: 30px 20px 35px #4A804E;position:relative;margin: 0 auto; /* added by dsonesuk - centres #body within parent element container(body) */}#manu{width:600px;height:100px;border:2px solid #179161;margin-top:1mm;/*margin-left:50px;*/margin: 0 auto; /* amended by dsonesuk - centres #manu within #body element container */position:relative;}

As long as you are not using styling like float, and the target element is a block element and a fixed width is set, these should centre horizontally across the screen.

[Voorm]

I tryed it,now is ok.Tnx.