please help me to review this site

The big empty blue header serves no real purpose, you should replace it with a title and description of what your site provides.

website is nice my suggestion is you gave lot of links its nice also provide some 1 or two lines details and read more button it will shows some content in the home page lot of empty space showing.

In my opinion, it is difficult to use. As already noted, the empty blue header is pointless. The word "mass" on the menu bar should be capitialized like the other menu items.

The real problem is below that is a sea of links which is not a usable or effective way to offer conversions. A visitor would have to wade through all of them, which they are not going to do, to find the conversion they might want to make.

Apparently, "Home" and "Length" are identical, which is rather pointless. On your home page you should not offer length conversions by default- you should welcome visitors to the site, tell them to click on the menu bar for the kind of conversion they want, maybe offer them a picture as eye-candy, and nothing more.

For each kind of conversion, you should not list all of the choices as clickable links. You should offer two drop-down boxes, one is A and the other is B. A represents what you are converting from, and B is what you want to convert to. This makes it simple and intuitive to select the kind of conversion.

Then, the visitor enters the value for A similar to the way you display a single conversion, and the result is shown. This part of your site, which does a specified conversion, is done very nicely.