What size should you make layouts

Ermmm,

Like pixels when ur designing in ps so it fits on most screens

I do mine; 800 x 700(mostly).

I usually use 950px for width, and height suitible for what I'm making.

When you make a new document select "Web" from the drop-down box then select one of the sizes. They are all the basic sizes for a website.

I do mine 800 x 600 but 950 x 670 if i'm making it special, which most of you guys dont see.

To be truely screen resolution friendly your site must be 760px wide or less. However in recent years the standard of site width has went up due to the change of default resolution from 800 x 600 to 1024 x 768. So you want to design in those dimensions (1024 x 768) however you make another image 900 x 768 and fill it with a colour like yellow or something then copy and paste it as a layer to the original. This means you then have a workspace as well as a view of how the site would look in an average users browser :)

I use these:

900x700
800x600

Or you could stop being lazy and just make fluid layouts that stretch to fit the entire screen and use whatever size you want.

750 px X 750 px for me.

I do them at 750x750 aswell