Sample form containing a preselected radio input

<form>
  <input type="radio" name="size" value="s" checked>small</input>
  <input type="radio" name="size" value="m">medium</input>
  <input type="radio" name="size" value="l">large</input>
</form>

The radio buttons will appear. They are labelled small, medium and large. The small radio option is preselected.

The values posted will be either s,m,l in the parameter size. Only 1 radio with the same name can be selected.