Remove button background

I have 2 button on screen. I need to remove background for only one button. But when i use below it removing all the button background. I need to use button skin for start button. I have another button is www.serverurl.net. Here i need to remove background skin.

using UnityEngine;
using System.Collections;

public class Aboutscreen : MonoBehaviour {

	// Use this for initialization
	void Start () {
	
	}
	
	// Update is called once per frame
	void Update () {
	
	}
	
	
	void OnGUI()
    {
		
		GUI.backgroundColor = Color.clear;
		
		
		 GUI.Label(new Rect(10f, 30f, 300f, 50f), "1.Print the alphabet image targets located at");
		
		 GUI.Label(new Rect(10f, 60f, 300f, 50f), "2.Point any of the animal images");
		
		 GUI.Label(new Rect(10f, 100f, 300f, 50f), "3.Finally your kids able to see the 3D animal render on the screen with soundss");
		
		
		if(GUI.Button(new Rect(260,15,120,50), "www.serverurl.net")) {
			
				
			
		Application.OpenURL("http://www.serverurl.net");
		}
		
		
		if(GUI.Button(new Rect(80,180,80,40), "start")) {
			
				
		 Application.LoadLevel("25Nov1");	
		
		}
		
		
	}
	
}

Just save and restore the background color:

using UnityEngine;
using System.Collections;

public class Aboutscreen : MonoBehaviour {

	void OnGUI() {
		Color c = GUI.backgroundColor;
		GUI.backgroundColor = Color.clear;

		GUI.Label(new Rect(10f, 30f, 300f, 50f), "1.Print the alphabet image targets located at");
		GUI.Label(new Rect(10f, 60f, 300f, 50f), "2.Point any of the animal images");
		GUI.Label(new Rect(10f, 100f, 300f, 50f), "3.Finally your kids able to see the 3D animal render on the screen with soundss");

		if(GUI.Button(new Rect(260,15,120,50), "www.serverurl.net")) {
			Application.OpenURL("http://www.serverurl.net");
		}

		GUI.backgroundColor = c;

		if(GUI.Button(new Rect(80,180,80,40), "start")) {
			Application.LoadLevel("25Nov1"); 
		}
	}
}

Alternately, you could reorder your button calls. I did the save and restore above because you cannot always reorder things when you are layering. But in this case:

using UnityEngine;
using System.Collections;

public class Aboutscreen : MonoBehaviour {

	void OnGUI() {

		GUI.Label(new Rect(10f, 30f, 300f, 50f), "1.Print the alphabet image targets located at");
		GUI.Label(new Rect(10f, 60f, 300f, 50f), "2.Point any of the animal images");
		GUI.Label(new Rect(10f, 100f, 300f, 50f), "3.Finally your kids able to see the 3D animal render on the screen with soundss");

		if(GUI.Button(new Rect(80,180,80,40), "start")) {
			Application.LoadLevel("25Nov1"); 
		}

		GUI.backgroundColor = Color.clear;
	
		if(GUI.Button(new Rect(260,15,120,50), "www.serverurl.net")) {
			Application.OpenURL("http://www.serverurl.net");
		}
	}
}

using UnityEngine;
using System.Collections;

  public class Aboutscreen : MonoBehaviour {
     

    public GUIStyle emptyButtonStyle;
     
     
    void OnGUI() {
      //now this button should transparent
      //whenever you assign emptyButtonStyle to a button that's background should transparent
      if(GUI.Button(new Rect(260,15,120,50), "www.serverurl.net", emptyButtonStyle)) {}
     
      //this button have no style assigned therefore its look like unity default button style
      if(GUI.Button(new Rect(80,180,80,40), "start")) {}
     
    }
  }