I'm not sure if we have a post with just a list of rules (I'll look), but posting links is definitely allowed. Are you copying the url and then inserting it via the 'insert link' button at the top? I'd have to check, but there may be a restriction in place. For example no links until you've made 5 or 10 or x number of posts. We've had huge spam problems in the past, which would explain such a restriction.
But for general information about how this forum works, have a look in at the top of the 'about this board' section the stickied threads have lots of good information:
About this board - Orchid Board - Most Complete Orchid Forum on the web !
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