ok, well, an example would be the name element:
<input type="text" name="name" id="name2" />
edit it to have a default value:
<input type="text" name="name" id="name2" value="Please Enter a Name" />
then add the onFocus and onBlur events:
<input type="text" name="name" id="name2" value="Please Enter a Name" onFocus="if(this.value=='Please Enter a Name')this.value='';" onBlur="if(this.value=='')this.value='Please Enter a Name';" />
the onfocus event:
onFocus="if(this.value=='Please Enter a Name')this.value='';"
checks to see if the value of the element is the default value, in this case "Please Enter a Name". if it is, then it clears the value and sets it to blank.
the onblur event:
onBlur="if(this.value=='')this.value='Please Enter a Name';"
checks to see if the value is blank, if it is, it sets it to the default "Please Enter a Name" value.