Independent column scroll in HTML page

Set a height for the columns, and set overflow: auto. You could also put all rules inside the same CSS selector. Like this:

#left, #right {
    float: left;
    width: 50%;
    height: 200px; /* Set your height here */
    overflow: auto;
}

The earlier postings improved a little:

• 100% html and body size .... without scroll bar
• margins for the left and right boxes
• individual scrollbars only when needed ("auto")
• some other details: Try it!

Fiddle: 2 independently scrolling divs

html, body {
  height: 100%;
  overflow: hidden;
  margin: 0;
}
#content {
  height: 100%;
}
#left {
  float: left;
  width: 30%;
  background: red;
  height: 100%;
  overflow: auto;
  box-sizing: border-box;
  padding: 0.5em;
}
#right {
  float: left;
  width: 70%;
  background: blue;
  height: 100%;
  overflow: auto;
  box-sizing: border-box;
  padding: 0.5em;
}

See this fiddle

#content, html, body {
    height: 98%;
}
#left {
    float: left;
    width: 50%;
    background: red;
    height: 100%;
    overflow: scroll;
}
#right {
    float: left;
    width: 50%;
    background: blue;
    height: 100%;
    overflow: scroll;
}

body {
  margin: 0;
}

#left {
  position: fixed;
  background-color: green;
  width: 50%;
  height: 100%;
  overflow: auto;
}

#right {
  position: fixed;
  background-color: red;
  width: 50%;
  height: 100%;
  right: 0;
  overflow: auto;
}

Please see this fiddle