Although I agree that the type is perhaps a little small, I think the main issue is that the tracking (space between the letters is a bit tight) and the leading (the space between each line of text) is very tight. The reason that it's hard to read (and still is even if you increase the size of text in your browser) is because when you have lines that long of text, they have to be further apart than you normally have them, or your eye skips between the lines and makes it hard to read. You may notice a lot of websites don't run the text from side to the other like that, they have a column down the side – it makes for shorter line lengths that are easier to read. The optimum number of words per line is 12 or so, if I remember correctly, and yours is over 20 per line.
Assuming you don't want to change the whole design by putting a column or a picture down the side (hence shortening the line length), if you increase the space between each line of text it will make it a bit easier to read. If you also increase the text size by one, the combination of these two things should make a big difference to the legibility. Hope that's helpful. 🙂
