No its not dangerous. Its actually recommended from time to time. Cookies are just little bits of info that get saved in your computer each time you go to website and helps it down download faster. Cookies can take up alot of space after awhile and i usually erase them once a week and do a full maintence on my computer.
The more practical way to increase the speed of your computer is to "Scan Disk" and then "Defragment"(Disk Defragmenter) it. These programs are located in system tools and both take time to work properly.
Yes I know, I haven't done that in months. I never have the patience. I will definetely do that tomorrow morning before I leave for work. That would be the best time. Or even before I go to bed. Thanks for the reminder Sonof SPazz. That totally slipped my mind.