There should be a print screen button on your keyboard (usually top right somewhere) and for any mac users who don't know it's apple + shift + 4

ok thanks. NikitaTech is investigating

can I check, just so we can eliminate possibilities, are you definitely using the 'preview' and 'post' buttons ie not typing and then hitting return?

We've tested the preview/posting in mumsnet classic and new and it seems to be working. Anyone still having this problem. Littlefish, sorry you're still having problems. Which computer/browswer etc are you using? Could you email us some screenshots of what's happening eg messages not wrapping round ads. Thanks

Sorry for delay spotting this! Will ask tech tomorrow. Anyone else having/has had this problem?