web  appication  testing  means  testing   the external 
link  &  internal  link   of  the  web   page.

Descriptive programming means nothing but loading the object
respository by writing code not by recording..

dp means without using repositury tool will identify the 
object using property values.
ex browser("name").page("name").webbutton("name")

for this line descriptive program is

browser("window id:=1005").page("window 
id:=22").webbutton("window id:=787")

we can use any property but that should be unique
here i used window id like that we can use any propery.

DP is advance topic in QTP. With out loding obj in repo... 
we can access them..... this is one of the example for that

systemutil.Run("http://www.rediffmail.com")

set BRO =Description.Create()
BRO("title").Value = "Welcome to Rediff.com India"
BRO("name").value ="Welcome to Rediff.com India"
BRO("openedbytestingtool").value= true


Set PG =Description.Create()
PG("title").value="Welcome to Rediff.com India"
PG("url").value="http://www.rediff.com/index.html"

Set UN =Description.Create()
UN("name").value= "login"
UN("Class Name").value ="WebEdit"
UN("type").value= "text"
UN("html tag").value="INPUT"

Set PWD =Description.Create()
PWD("name").value ="passwd"
PWD("Class Name").value="WebEdit"
PWD("type").value="password"
PWD("html tag").value="INPUT"

Set Login =Description.Create()
Login("name").value ="Go"
Login("Class Name").value="WebButton"
Login("type").value="submit"
Login("html tag").value="INPUT"
Login("value").value="GO"
Login("class").value="rmailgobtn"

temp= Browser("Welcome to Rediff.com").Page("Welcome to 
Rediff.com").WebElement("ShockwaveFlash1").Exist
If temp= true Then
    'Browser("Welcome to Rediff.com").Page("Welcome to 
Rediff.com").WebElement("ShockwaveFlash1").
End If


Browser(BRO).Page(PG).WebEdit(UN).Set "shyam_sad" 
Browser(BRO).Page(PG).WebEdit(PWD).Set "7shyam" 
Browser(BRO).Page(PG).WebButton(Login).Click