Hi I just created a website that helps people learn Javascript, HTML and other techniques used to make websites.

www.htmlhandbook.tk

Please give me feedback on how good/professional-looking the site is. Also please send me suggestions of what else to put on my site to make it look better.

Thanks.

Just a quick review, but...

h1, h2, etc. are headings, not "font sizes".

Your examples use invalid markup.

The alt attribute of the img element is required. See also Use of ALT texts in IMGs.

If you specify a background image, then you should also specify foreground colors to assure adequate contrast. If you specify foreground colors, then you should also specify the background color, to assure adequate contrast.

color=92DB70 should be color=#92DB70 (and so forth).

Where did you get method="link" ? HTML 4 allows only method="get" and method="post". HTML 5 also allows method="put" and method="delete". But I don't see anything about method="link".