As a web developer, it can be quite time consuming to meticulously code complex pages with HTML and CSS. What’s worse is to invest a lot of time doing that and then realizing that your precious layout just doesn’t work from a UX stand point. Sometimes you have multiple ideas for a layout and are torn between which one to go with.
There are many software tools out there which allow you to create wireframe mockups/sketches of user interfaces. Some of these tools can be quite expensive and for a startup that is bootstrapping, totally out of reach. Luckely, there's an inexpensive tool called Balsamiq Mockups For Desktop which really increased the productivity as a designer
Mockups For Desktop is based on the Adobe AIR platform. Once you install the AIR runtime on your PC, installing AIR-based applications is a breeze.
The elements are very simple to position with intelligent snap-to-grid alignment. Double-clicking an element allows you to edit its text content. You can also modify and fine tune the properties of each element by using the hovering property editor that shows up when an element has focus.
I use this tool a lot for creating functional analyses. And I must say: I love it! :-) ! Demo online is totally free, and you can export your mockups into XML format. So it's very easy to continu working on them. You can also save the mockups as PNG and PDF.