buzibuzi wrote:it seems the iframe is causing this, because when removing it, the page is saved fine.
any ideas why ? how to solve this ?
This is almost certainly a "rule" in your host/server
firewall implementation (likely mod_security). It would be logical from a security-perspective to block <iframe> tags from POST requests to your server, as iframe's could include malicious content. This however has no benefit of course for your X3 Panel, where only you or people you trust has access ...
You could ask your host to disable the firewall (or some rules), from below your /panel/ URL segment.
The only other option would be to create "hacks" in X3 to generate correct <iframe> html code from a fake placeholder (for example <div class=iframe> ) ... We already did something similar to <input>, which was blocked on some other servers firewall. However, this is undesirable for reasons needless to mention.