hello friend i'm want to build a website.......i have no more topic i have only one topic AutoCAD......... and i build a website on this topic is it right topic or wrong.......... tell me the best topic ,......and i earning money
The best topic is always one that you have knowledge of and are passionate about. Now you just have to work out if you can do a better autocad blog than all the people who currently do autocad blogs. Picking a new topic would be foolish if you are inexperienced because you'd be learning a subject and fighting for market share with people far more experienced than you. Remember to write a business plan or all those hours may be wasted.
Use search (on the forum, a search engine and other useful sites) to find information and learn. Really, the first thing is you need to learn to use your own brain, think for yourself. sarahk already gave you a lot of good pointers, so research them. You won't get anywhere without trying.