Error while writing articles with HTML CODE inside

I’ve started posting of code segments in my WP-blog, and found very inappropriate possibility to crash my blog. Just write incorrect tag to body – and blog crashes.
I’ve tried to solve problem – replaced all occurencies < and > with (& g t ?? and (& l t ;).
It works – but i can’t EDIT posts – cause when watching text of article – it shows – < and > symbols, NOT PREVIOUSLY wrote there!