Gap at top of page despite margin:0 and padding: 0

Question

There's a 32px gap at the top of my site, despite setting margins and paddings to 0. I know it's 32px because I can fix it with padding: -32px. But then I have a gap at the bottom! In Firebug, it seems the body only start 32px down from the beginning of the HTML element, even though I've set margins and paddings to 0.

Here's my CSS:

html {
  height: 100%;
  padding: 0;
  margin: 0;
}

body { 
  background-color: #a7a9ac; 
  color #666666;
  background-image: url('body-bg.gif');
  background-repeat: repeat-x;
  height: 100%;
  padding: 0;
  margin: 0;
}

body, p, ol, ul, td {
  font-family: verdana, arial, helvetica, sans-serif;
  font-size:   13px;
  line-height: 18px;
}

.container_banner h1{
  font-size: 48px;
  position: relative;
  top: 130px;
  left: 250px;
  width: 400px;
}

.container_banner h3{
  position: relative;
  top: 0px;
  left: 32px;
  font-size: 10px;
  color: #F8F8F8;
}

.container_banner{
  position: relative;
  top: 0px;
  background-image: url('banner.png');
  background-repeat: no-repeat;
  margin: 0 auto;
  width: 945px;
  height: 188px;
  padding: 0px;
  background-color: #ffffff;
}

.container{
  position: relative;
  top: 0px;
  margin: 0 auto;
  min-height: 100%;
  width: 945px;
  padding: 0px;
  padding-top: 20px;
  margin-bottom: 0px;
  background-color: #ffffff;
  background-image: url('thin-background.png');
}

.content{
  margin-top: 0px;
  margin-left: 30px;
  min-height: 100%;
}

Container banner is the topmost div, followed by container (which includes content).

Answer 1

I think this is caused by the use of position: relative and your h1 element inheriting a margin by default. When you use position: relative, the margin does not seem to be shifted with the actual content and therefore gets applied to the top of the page.

I have changed the relevant CSS to fix this:

.container_banner h1{
  font-size: 48px;
  position: relative;
  top: 130px;
  left: 250px;
  width: 400px;
  margin-top: 0;
}

You may need to do the same for any other elements that are set to position: relative and have a margin (e.g. h3 tags)

It would be best to cut down on the use of position relative as it is somewhat difficult to predict such behaviour.