What do you call a person who loves to sit in front of the computer?

Solution 1:

From merriam-webster.com:
mouse potato (noun) slang
: a person who spends a great deal of time using a computer

Solution 2:

I personally think Dian's answer is brilliant, but if you're looking for a more technical word (excuse the pun), you might consider "technophile".

technophile (noun)
a person very enthusiastic about technology, especially one who enjoys the advances in computer and media technology.

http://en.wiktionary.org/wiki/technophile

It's not precisely someone who sits in front of a computer all day, but one would expect that to be inferred.

Solution 3:

A (computer) nerd or geek, perhaps?

Note that the connotations of both of these terms may vary between different regions and social groups, and that both may be considered pejorative to varying degree. (Indeed, this is likely to be true to some extent of any term describing a lifestyle or a group of people which some others may hold in contempt.) Also note that both terms can have the broader meaning of "a person deeply interested in a particular subject, often to the point of limiting social interaction", and that, depending on context and the reader's/listener's background, the default subject may or may not be assumed to be specifically computers.

Solution 4:

While one could use terms such as Geek, mouse potatoe, Technophile, or Computer Whizz, these are all subjective, and regional.

e.g. a mouse potatoes would be thought of as a kind of potatoe in the UK, most likely to elicit the question what do they taste like? and a technophile could be someone obsessed with technology despite not owning a desktop computer.

So there are no words that fit directly into what you want reliably, that aren't in some way ambiguous, culturally dependant on location, or overlapping elsewhere.

Instead, it's better to use the words classifying people based on what they do on their computers. e.g. blogger, graphics designer, gamer, programmer, typist, etc