Either you are a newbie or a professional in WordPress flatform, free themes are always a considered resource when you carry out a new blog.
Free WordPress themes, are popular because of their appealing designs and their ease of installation and use.
They're great tools to use when you launch your new blog, and if you dabble a bit in graphic design and CSS (Cascading Style Sheets), you can customize one of the free WordPress themes to fit your own needs.
By using free themes, you can have your blog up and running with a new design - without the help of a professional - pretty fast.
And with thousands of themes available, you can change your theme as often as you want.
These themes are free, period.
You can download and use them on your Website at absolutely no cost.
It's a courtesy to include a link to the designer in the footer of your blog - but you can even remove that link if you want to.
But there is also a disadvantage you may got if you use a free theme, unsafe themes.
Unsafe themes, on the other hand, are developed by people who are looking to take advantage of the blog owners who use them.
They may have

• Spam links: These links usually appear in the footer of the theme and can link to some pretty unsavory places.
  The designers of these themes hope to benefit from traffic from your site.
  They count on the idea that most blog owners won't notice the links or know how to remove them.
  
• Malicious code: Unscrupulous theme designers can, and do, place code in theme files that inserts hidden malware and/or virus links and spam.
  Sometimes, you see a line or two of encrypted code that looks like it's just part of the theme code, and unless you have a great deal of knowledge of PHP, you may not know that the theme is infected with dangerous code.
  

The results of these unsafe theme elements can range from simply annoying to downright dangerous, affecting the integrity and security of your computer and/or hosting account.
To protect yourself from unsafe free themes threats you should download free themes from trusted sources.
For this reason, the official WordPress Theme Directory is considered to be a safe place from which to download free themes.
WordPress designers develop these themes and upload them to the theme directory, and each theme gets vetted by the folks behind the WordPress platform.
In the official directory, themes that contain unsafe elements are simply not allowed to play.
So you know you're getting a clean, quality theme for your blog.
You can rest assured that themes from the official directory are safe, and free of spam and malicious code.