Error after changing the web configuration file of ASP web applications

Hello all,
I have been trying to link the ASP web applications. I successfully changed the web configuration file, but after this, an error was seen on my screen. The screenshot of the error is as follows:

As you all can see that line # 12 has been highlighted. So, I removed this line and again tried to configure this file,
but it ended up in another error which is attached below:

Now this is highlighting another line. What should I do? I suppose, this is an ongoing activity.
What do you all suggest?
Waiting for your helpful suggestions.
Regards.
