Describe the issue you are having including any error messages / problems you are seeing. Describe as fully as you can the steps for reproducing this issue. The key to fixing any issues is reproducability. Anything our developers can reproduce should be fixable, anything we can't is very hard to fix!
Don't forget to tell us which platform you were using - Mac / Windows or a Tablet device, and which browser.
You can upload screen shots which is also a big help. See these instructions for Windows users or these instructions for Mac users to see how to capture a screenshot for uploading.
Finally, tell us if you are happy for a member of our team to contact you about your issue for further information or to get you to test a fix we have implemented.