I use Mozilla Firefox and have no problems - those that seem to be having the most problems are the ones using IEI
sometimes get the message asking if I want to leave the current page- that just means you are sending a message and leaving the page you are on, just click yes.
To start a new thread- go to the top- click on home- then the section you want to start the new topic in- click on start new topic and you are good to go
For selling items you have to have the add approved by a moderator- Remember we all are volunteers and have regular paying jobs so sometimes we don't get to them as fast as everyone would like- as long as the add is allowed following the rules, just be patient and it will appear
Have I missed any questions ?