I would suggest you that instead of trying to be jack of all trades, you choose to be the master of a few that are relevant. I assume you don't have any kind of development experience so this is the route I suggest -
1. Frontend - Learn HTML 4/5, CSS 2/3, JavaScript, XML, JQuery/JQuery UI (or any library of your choice). Read books, online tutorials etc to learn the basics and then practice the skills by developing front-end part of your startup idea. This will help in not only polishing your web designing skills but you will also have a working HTML Prototype of your web application.
2. Backend - Learn only one backend programming language. Choose from Python/PHP/Ruby/Java. If you want to take easy but good enough route learn PHP. If you want to choose the best, learn Python/Ruby. While learning the backend programming language, at some stage, you will be required to learn database technologies - SQL (MySQL), or NoSQL(CoucheDB, MangoDB etc). When you feel comfortable with your skill level, take the html mockup developed in first stage and implement its backend to have a fully functional prototype of your application.
3. Frameworks(optional) - Though step one and two are enough to help you develop your application, it is always good to know a good framework for your language of choice. I would suggest codeigniter for php, Django for python and Ruby for rails. For practice, try re-implementing your application in the chosen framework.
4. Mobile Technologies(optional) - It is important if you plan to have a mobile version of your application. You have many options here. Start with Android/Java and then ios/objective-c. Develop the mobile version of your application.
1. Frontend - Learn HTML 4/5, CSS 2/3, JavaScript, XML, JQuery/JQuery UI (or any library of your choice). Read books, online tutorials etc to learn the basics and then practice the skills by developing front-end part of your startup idea. This will help in not only polishing your web designing skills but you will also have a working HTML Prototype of your web application.
2. Backend - Learn only one backend programming language. Choose from Python/PHP/Ruby/Java. If you want to take easy but good enough route learn PHP. If you want to choose the best, learn Python/Ruby. While learning the backend programming language, at some stage, you will be required to learn database technologies - SQL (MySQL), or NoSQL(CoucheDB, MangoDB etc). When you feel comfortable with your skill level, take the html mockup developed in first stage and implement its backend to have a fully functional prototype of your application.
3. Frameworks(optional) - Though step one and two are enough to help you develop your application, it is always good to know a good framework for your language of choice. I would suggest codeigniter for php, Django for python and Ruby for rails. For practice, try re-implementing your application in the chosen framework.
4. Mobile Technologies(optional) - It is important if you plan to have a mobile version of your application. You have many options here. Start with Android/Java and then ios/objective-c. Develop the mobile version of your application.