Pretty clean and easy on the eyes.
However, I would definetly change the Longin|Sign Up part. Change it, perhaps, to just Login. It could say, on the login screen at the bottom, 'Don't have an Account? Register here' kind of thing. Would be better.

Not too bad, I'd recommend spacing the text in your 'welcome' 'about' and 'social media' text boxes a bit lower, it looks weird as the text is nearly overlapping the top of the box.

Gonna seem harsh but....

Text is bad against a gradient gray background
Spelling is atrocious
Your links in the top right wouldn't be level with the address bar
Everything is a bit too flat, this work if done correctly but not in this case.
The arrow is too prominent.

Yes its your first design and I appreciate that. Time to start looking at tutorials and inspiration.
Use colour wheels to find which colours compliment each other and how to layout a site.

Web design can be a tricky one, and this just wont cut it. Like Pish said, I'd recommend looking at both tutorials for making nice graphics for websites and how to style them accordingly. Making website designs in Photoshop is a whole lot different to implementing them in code, so depending on how far you plan on taking your work really is up to you.

Feedback for the work above:

Text - Way to big and bold for the type of website this is, look into using sans serif fonts as they'll always render better for web design. Also lose the gradients.
Background - Lose the gradients, it's way too "in your face" . A simple dark pastel colour would fit nicely there.
Layout - The layout itself is decent, I've used it a few times in previous projects myself, or something very similar, but the execution of it is poor. Lose the arrow to scroll though tabs, unless you have a valid reason for it being there, you'll never use it.

Put the social links at the bottom, I'd personally never put them at the top as they'd just draw people's attention away from what's on the site. Use smaller icons for them also, preferably single coloured ones, like Font Awesome, ect.

I use this site: [ Register or Signin to view external links. ] to explore colour palletes that might fit with the design I want, maybe it could help you out and explain why I said what I did above.