I wanted you to know that the hard-coded fonts and cursor in the web page makes someone who has a dark theme installed (in my case in Ubuntu 9.10 with Firefox as a browser) impossible to read what is typing while posting a message.
Although it is not a crucial thing (I can write the whole message in a text editor and then copy and paste it into the selected place), it makes using the website use a little harder than it should be.
I guess you might be a way to solve this problem because I don't have it with other web pages.
I am attaching an image for you to see the effect.
Change the theme ? It looks like your theme draws UI components with a black background. The equivalent of using background-color: 000000 Do you see this with other themes ? Also how do other web sites and text boxes behave under this theme ?