again let me clearly tell you this web site contains many link pick any one that will be help full to you.now i am making some structured urls from which you can easily learn many things .remember these are all for technical purpose only :).
so here we go for Web application security part.
Learn the fundamental/primary attacks.
-XSS(cross site scripting )
-CSRF(Cross Site request Forgery)
Many beginner find this slight difficult to understand so here below link for simple explanation.
Remote Code/Command Execution
XML external entity attack
Other few popular attacks on web application
Of Course there exist bugs in mobile application too so if you are interested on that you will definitely find the link more likable
Android Security learning
iOS application testing
For Advance security researchers you can follow the VULNHUB It s grate source of learning.
Another important website for learning is infosecinstitute that is great place for all type of learner.
Lab For practice
Please do comment if you have more useful link and thanks have a nice day keep learning :)