Where to report bugs?

There seems to be an Editor issue in Landscape - target layers, where the scroll bar cannot scroll as low as the last layer. This applies whether the editor is normal or maximised. It is very frequent though intermittant. I have 12 layers in total, but only 9 invariably can be reached. Clearly this seems like an interface bug and so has very little purpose in questions or discussions but presumably there is a seperate location to post bugs? Can anybody advise me - thanks.