I wanted to fetch a specific data from a website and display in a label in my app. Suppose there is a website where data changes everytime like weather forecast website.
I just want to fetch data whenever someone open the app. I want to fetch Temperature from that website. How to do that WITHOUT API system
Use the web site address in web componet block, specify that exact path to the app, then it will give you the out put ti the label ,
You mentioned that you want to get the weather. This can be of some help to you.
Welcome to the Community, have a nice time Koding 
I am new to this can you help me with accurate blocks.
please do the tutorials to learn the basics and try something yourself… then if you got stuck, post a screenshot of your relevant blocks to get help…
A very good way to learn App Inventor or Kodular is to read the free Inventor’s Manual here in the AI2 free online eBook App Inventor 2 Book: Create Your Own Android Apps … the links are at the bottom of the Web page. The book ‘teaches’ users how to program with AI2 blocks.
There is a free programming course here Course In A Box and the aia files for the projects in the book are here: App Inventor 2 Book: Create Your Own Android Apps
How to do a lot of basic things with App Inventor are described here: How do you...? .
Also do the tutorials Tutorials for MIT App Inventor to learn the basics of App Inventor, then try something and follow the Top 5 Tips: How to learn App Inventor
Taifun
What is he supposed to do if he constantly require a username and token on his web address?