Hi Luc.
Busy professionals are very fussy customers. Time is money to them and they don't like things to be different!
The site looks okay. Green is a very conservative colour and is usually associated with finance etc., so the choice of colour is good. I don't have a problem with the font size as there's not a huge amount of text and many people - especially the older generation - keep complaining that text on the web is too small!
There's *way* too much dead space though! Your top section is huge and the only thing in there is a logo, which is quite small. I'd make the logo bigger and reduce the size of the top area to the absolute minimum to hold it. The left section is pretty much the same thing, except there's nothing in there that is useful! I'm not saying ditch it though, as it helps to balance the site. What I'd recommend is that you move it to the right-hand side so that your navigation is on the left, where you'd expect it, and the graphical bit is out of the way, but still adding to the overall look of the site. Finally, where you've wrote 'Business & social networking', it really doesn't stand out. It will help if you drop the 'Welcome' message and move the other wording to the left along with the navigation etc., but you'll also want to make it bolder so that it stands out more.
The title of your homepage is 'Welcome!' too. When someone bookmarks your site is will appear in their list as just that, 'Welcome!'. Not very memorable! Change the page title to 'Innotara - Business and Social Networking'. That way it will bookmark under 'I' for Innotara, again where you'd expect it, and it includes a reminder of what the site is about.
With a few changes I think your good site will be a great site
