Why does my dissappear?

WordPress does remove style tags. While it allows HTML to some degree in post content, it’s not really meant for full range of it. It’s a content, not markup data.

You could use tiny_mce_before_init filter to adjust extended_valid_elements for TinyMCE instance.

See this answer on SO for some examples.

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)