HTTP error 400 : fat cookie

[Whisno]

Hi,
I did get an HTTP error 400 when requesting the index page because a cookie was too big.
I forgot to note the cookie's name before I deleted it but its value was

%7B%22channel_custom%22%3A%7B%22__elgg_token%22%3A%22e4f82c4983472bf3cdd8b58ccb109242%22%2C%22__elgg_ts%22%3A%221434743131%22%2C%22background_repeat%22%3A%22no-repeat%22%2C%22background_attachment%22%3A%22scoll%22%2C%22background_colour%22%3A%22%22%2C%22h1_colour%22%3A%22%22%2C%22h3_colour%22%3A%22%22%2C%22menu_link_colour%22%3A%22%22%2C%22social_link_fb%22%3A%22%22%2C%22social_link_twitter%22%3A%22%22%2C%22social_link_gplus%22%3A%22%22%2C%22social_link_tumblr%22%3A%22%22%2C%22social_link_linkedin%22%3A%22%22%2C%22social_link_github%22%3A%22https%3A%5C%2F%5C%2Fgithub.com%5C%2FWhisno%22%2C%22social_link_pinterest%22%3A%22%22%2C%22social_link_instagram%22%3A%22%22%2C%22social_youtube_input%22%3A%22%22%2C%22briefdescription%22%3A%22%22%2C%22website%22%3A%22http%3A%5C%2F%5C%2Fwww.whisno.be%22%2C%22location%22%3A%22%22%2C%22contactemail%22%3A%22%22%2C%22description%22%3A%22%22%2C%22container_guid%22%3A%22%22%2C%22guid%22%3A%22458714937468923904%22%2C%22submit%22%3A%22Save%22%7D%7D  

It seems to be the channel customization, but why store it in a cookie ?